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Screening Tests and Pre-Anaesthetic Bloodwork in Veterinary Patients: Issues & Evidence

Posted on March 13, 2013 by skeptvet

A perennially hot topic in human medicine is the risks and benefits of screening tests. Blood tests, imaging (like CT scans) and other diagnostic tests are usually seen by the general public as only beneficial. How could it be a bad thing to detect a disease, even before it is causing any symptoms? The reality, of course, is that such tests come with risks as well as benefits, like everything else in medicine.

I’ve written a bit about screening tests before, and I wrote an enthusiastic review of Gilbert Welch’s book Over-Diagnosed, which I believe should be required reading for anyone who is a healthcare provider or patient. The previously underappreciated dangers in inappropriate diagnostic tests have driven significant and sometimes controversial recommendations from the United States Preventative Services Task Force (USPSTF), the federal agency responsible for generating evidence-based guidelines concerning preventative medicine. And a broad coalition of medical specialty groups have formed an organization called Choosing Wisely which is dedicated to promoting sensible use of diagnostic tests by education physicians and the public about the risks and uncertainties, as well as the benefits, of such testing.

In general, the benefits of screening tests involve either allowing a disease to be treated at an earlier stage, even before the patient is aware of having it, and thereby improving the long-term outcome, or detecting risk factors for diseases which can be managed to reduce the chances of those diseases developing at all. For this to work, of course, the tests must screen for something which is treatable or preventable. A test which warns you in high school that you will die of some horrible disease in 30 or 40 years, and that there is nothing you can do about it, isn’t beneficial. In fact, it is more likely to do harm in that it generates anxiety and affects how you live your life in ways that don’t make you any healthier or happier.

Effective screening tests must also be accurate enough that they don’t miss a lot of cases of real disease or indicate disease is present in a lot of people when it really isn’t. No test is perfect, but most medical screening tests can be evaluated in people know to have, or not have, the condition tested for, which can give us an idea how accurate a particular test is. This generates the “sensitivity” and “specificity” numbers often cited to identify how reliable a test is.

For statistical reasons I won’t get into, these numbers can be misleading. Even a test which very rarely misidentifies someone as having a disease they don’t actually have will still misidentify a high proportion of people tested if the disease is really rare. So even the best tests aren’t very useful if we test people who are very unlikely to actually have the disease we are looking for. This is one reason why indiscriminate use of diagnostic tests is a not effective or reliable.

The devil, as always, is in the details, so it is difficult to generalize about when screening tests should or shouldn’t be used. For the most part, the guidelines in humans recommend using most screening tests only when there is some reason to suspect the disease one is looking for is present. If a person has typical symptoms, or is in a demographic group known to be frequently affected by the disease of interest, then a screening test might make sense.

Testing women for prostate cancer with a blood test such as the PSA, for example, is obviously ridiculous. The disease is never going to be present. And even with very good tests, false positives can show up, so what would a doctor do with such a positive test result? Most cases aren’t this clear cut, of course, but the same logic applies for all screening tests. The more likely the disease is to be present, the more reliable a positive test result is. And the less likely the disease is to be present, the more we can trust negative results. So choosing rationally who to test is a very important part of getting reliable results.

So what are the risks of screening test? Well, I’ve already touched on one—the unproductive anxiety associated with being misdiagnosed or with being correctly diagnosed with a disease you don’t have. Many people this hasn’t actually happened to will say they aren’t worried about this and would want to be tested even if this is a possible risk. However, people who have had the experience of a mistaken diagnosis, or a diagnosis they can’t do anything about, describe it as a terrible, life-altering experience. In veterinary medicine, this anxiety is unlikely to affect our patients directly. But there is no question it can profoundly affect their owners, as well as how their owners treat their pets, so this is still a risk to consider.

A more tangible risk of misdiagnosis is the danger and discomfort associated with unnecessary follow-up tests or treatment. Thousands of men have been seriously harmed by unnecessary testing and treatment for prostate cancer that they either never had or that would never have made them ill. This is one of the examples that has driven the more cautious and rational approach to screening tests in humans, and it is relevant to veterinary patients as well. If we diagnose disease that aren’t there, we are inevitably going to harm, and even kill, patients who would have been better off if we had not tested them in the first place. This risk has to be recognized and appropriate steps taken to minimize it, including using tests in a rational, evidence-based way.

And though it seems unpopular in America to acknowledge that it matters, the cost of unnecessary testing is a real issue. In human medicine, healthcare costs are a significant economic burden with widespread harm throughout the economy. And in veterinary medicine, where euthanasia is often chosen when money for further testing or treatment runs out, wasting money on unnecessary tests can easily lead to an inability to provide care that is actually needed.

As usual, the evidence concerning the risks and benefits of screening tests, and the attention given to the issue, are far less in veterinary medicine than in human medicine. However, there is some research evidence looking at screening tests in veterinary patients. Given the aggressive push from the AVMA for more preventative care, which is not a transparent, evidence-based effort and which in some ways appears driven as much by concern about revenue as concern about patient welfare, it is worthwhile to consider the issues involved in recommending screening tests for veterinary patients.

The most common and widely recommended screening tool is the annual physical examination. In human medicine, there is growing doubt about whether physical exams of apparently healthy people is useful or beneficial. There is almost nothing in the way of controlled research on the subject in veterinary medicine.

Certainly, every vet can think of examples of a patient whose owners were not aware of any problem but who turned out, after a good physical exam, to have a serious illness. We are most likely, of course, to remember those examples in which the illness was treatable, since happy endings that make us feel good about the work we do tend to stick in our minds. We may or may not remember cases in which the illness we identified couldn’t be treated or was treated in a way that did little to improve the well-being or longevity of the patient and perhaps even made it worse due to side effects of the treatment. And, of course, we can’t possibly remember those cases in which a client declined to accept the initial test or follow-up investigation and treatment and the disease never materialized. Our memory of individual cases is not, unfortunately, a very reliable way to decide whether physical exams of apparently health pets are beneficial to our patients or not. Availability bias, confirmation bias, cognitive dissonance, and many other cognitive quirks make such anecdotes deeply misleading.

One obvious difference between human and veterinary medicine is that people can tell their doctors about symptoms they experience which might suggest a disease even when there is no outward sign of one. Our pets have a much more limited ability to make known how they feel, and in fact may act8ively hide signs of illness from us. This supports the argument that physical exams, and other diagnostic tests, may be justified in apparently healthy pets even when they aren’t in apparently healthy humans. However, as reasonable as such an argument is, it remains unproven.

The other kind of diagnostic test frequently recommended is bloodwork. There is absolutely no consistency within the profession on what kind of screening blood tests should be done when, how often, and in which patients. It is common to recommend some kind of bloodwork before anaesthesia, and often on some regular basis in older pets, but there are few guidelines, those that do exist are based on opinion and experience rather than high-quality evidence, and individual veterinarians and hospitals vary widely in their recommendations.

There have been a couple of studies looking at how often abnormalities are detected on pre-operative bloodwork, and to a lesser extent whether these abnormalities affected the treatment the patient received. I will discuss a couple of these, which I think fairly represent the state of the evidence at this time.

Alef, M.; Praun, F. von; Oechtering, G. Is routine pre-anaesthetic haematological and biochemical screening justified in dogs? Veterinary Anaesthesia and Analgesia 2008 Vol. 35 No. 2 pp. 132-140

Abstract
Objectives: To determine if routine haematological and biochemical screening is of benefit in dogs requiring anaesthesia and to establish the most useful tests for pre-anaesthetic risk assessment. Animals: One thousand five hundred and thirty-seven client-owned dogs undergoing surgery at the University of Leipzig between January 2003 and April 2004.

Materials and methods: After obtaining a standardized history and a physical examination, all dogs requiring anaesthesia were assigned to an ASA physical status group, their needs for pre-anaesthetic therapy determined and an anaesthetic protocol proposed. Haematological (haematocrit, red blood cell count, white blood cell count, platelet count and haemoglobin concentration) and serum biochemistry tests (plasma urea, creatinine, glucose, total protein, sodium and potassium concentration; serum alanine aminotransferase, alkaline phosphatase and lipase activity) were then performed in all animals. The results of these were then used to: (1) re-define each dog’s ASA physical status; (2) determine any altered requirement for pre-anaesthetic therapy; (3) re-determine the suitability of the dog to undergo surgery; and (4) re-examine the suitability of the original proposed anaesthetic protocol.

Results: The history and clinical examination in 1293 out of 1537 dogs (84.1%) revealed that haematological and biochemical tests would have been considered unnecessary under normal conditions. Of these, 63.9% were categorized as ASA 1, 28.5% as ASA 2, and 7.6% at higher risk. In some dogs, screening tests showed abnormal results: 16.7% of 1293 dogs had abnormal plasma urea levels, with 5.9% of values above the reference range. However, only 104 dogs (8%) would have been re-categorized at a higher physical status category had the laboratory results been available. Additional screening data indicated that surgery would have been postponed in 10 dogs (0.8%) additional pre-anaesthetic therapy would have been provided in 19 animals (1.5%) and the anaesthetic protocol altered in two dogs (0.2%).

Conclusion: The changes revealed by pre-operative screening were usually of little clinical relevance and did not prompt major changes to the anaesthetic technique.

Clinical relevance: In dogs, pre-anaesthetic laboratory examination is unlikely to yield additional important information if no potential problems are identified in the history and on physical examination.

This study fairly clearly shows that only a very small number of dogs presenting for surgery with no reason to suspect illness actually show abnormalities on screening bloodwork, and these abnormalities almost never influence the care these dogs are given. Of course, the question remains open whether testing thousands of dogs to identify relevant problems in maybe 2% is appropriate. Do the benefits for a few individuals (whatever those are, since the study didn’t actually look at the outcome of the procedure) outweigh the costs, the risk of misdiagnosis, harm from unnecessary follow-up testing or unnecessary deferral of needed surgical procedures, and the stress to the owners of dogs who are misdiagnosed?

Another similar study looked at a population for which there is a reasonable rationale to performing pre-operative screening; geriatric dogs.

K E Joubert. Pre-anaesthetic screening of geriatric dogs. J S Afr Vet Assoc. March 2007;78(1):31-5.

Introduction: Pre-anaesthetic screening has been advocated as a valuable tool for improving anaesthetic safety and determining anaesthetic risk. This study was done determine whether pre-anaesthetic screening result in cancellation of anaesthesia and the diagnosis of new clinical conditions in geriatric dogs.

Methods: One hundred and one dogs older than 7 years of age provided informed owner consent were included in the study. Each dog was weighed, and its temperature, pulse and respiration recorded. An abdominal palpation, examination of the mouth, including capillary refill time and mucous membranes, auscultation, body condition and habitus was performed and assessed. A cephalic catheter was placed and blood drawn for pre-anaesthetic testing. A micro-haematocrit tube was filled and the packed cell volume determined. The blood placed was in a test tube, centrifuged and then analysed on an in-house blood analyser. Alkaline phosphatase, alanine transferase, urea, creatinine, glucose and total protein were determined. A urine sample was then obtained by cystocentesis, catheterisation or free-flow for analysis. The urine specific gravity was determined with a refractometer. A small quantity of urine was then placed on a dip stick. Any new diagnoses made during the pre-anaesthetic screening were recorded.

Results: The average age of the dogs was 10.99 +/- 2.44 years and the weight was 19.64 +/- 15.78 kg. There were 13 dogs with pre-existing medical conditions. A total of 30 new diagnoses were made on the basis of the pre-anaesthetic screening. The most common conditions were neoplasia, chronic kidney disease and Cushing’s disease. Of the 30 patients with a new diagnosis, 13 did not undergo anaesthesia as result of the new diagnosis.

Conclusions: From this study it can be concluded that screening of geriatric patients is important and that sub-clinical disease could be present in nearly 30 % of these patients. The value of screening before anaesthesia is perhaps more questionable in terms of anaesthetic practice but it is an appropriate time to perform such an evaluation. The value of pre-anaesthetic screening in veterinary anaesthesia still needs to be evaluated in terms of appropriate outcome variables.

This study appears to find more real and meaningful abnormalities, as one would expect in an older population. However, the details still showed that age did not reliably predict which dogs would have bloodwork abnormalities:

The effect of age and/or breed on the choice of pre-anaesthetic laboratory testing was not fully elucidated in the current study. However, preliminary results show only statistically significant differences (p < 0.05) in platelet count and ALT activity in dogs over 10 years of age. No consistent differences could be found between age groups (<2, 2–7, 7–10 and over 10 years) for the plasma concentrations of glucose, urea and lipase activity. Young dogs (<2 years) showed statistically significant but only slight differences to other age groups in total protein and sodium concentration.

Furthermore, there was no detectable difference in the chances of a pre-operative abnormality in dogs that did or did not have complications during surgery, so it is questionable whether the abnormalities that were found actually helped prevent problems from surgery (though this might have been affected by the deferral of surgery in dogs with some detected abnormalities):

Laboratory test results were within the reference range or interpreted as being clinically irrelevant in 21 of 25 dogs experiencing complications. Relevant laboratory findings were found in only four. The incidence of adverse incidents was 3.8% in dogs with ‘abnormal’ laboratory results and 1.8% in animals with ‘normal’ values. Because of the limited number of complications, no statistical difference could be shown between groups.

Certainly, more research is needed on this topic. However, the existing research suggests that routine pre-operative bloodwork is likely to benefit only a very few patients, so the questions about whether this justifies the costs and risks is still not easy to answer.

In human medicine, guidelines for pre-anesthetic screening are more conservative that what is routinely done by veterinarians:

The guidelines from the American Society of Anesthesiology Task Force on Pre-anesthetic Evaluation state the following:

Routine Preoperative Testing
• Preoperative tests should not be ordered routinely.
• Preoperative tests may be ordered, required, or performed on a selective basis for purposes of guiding or optimizing perioperative management.
• The indications for such testing should be documented and based on information obtained from medical records, patient interview, physical examination, and type and invasiveness of the planned procedure.

Preanesthesia Hemoglobin or Hematocrit
• Routine hemoglobin or hematocrit is not indicated.
• Clinical characteristics to consider as indications for hemoglobin or hematocrit include type and invasiveness of procedure, patients with liver disease, extremes of age, and history of anemia, bleeding, and other hematologic disorders.

• Preanesthesia Serum Chemistries (i.e., Potassium, Glucose, Sodium, Renal and Liver Function Studies)

• Clinical characteristics to consider before ordering preanesthesia serum chemistries include likely perioperative therapies, endocrine disorders, risk of renal and liver dysfunction, and use of certain medications or alternative therapies.

• The Task Force recognizes that laboratory values may differ from normal values at extremes of age.

• Preanesthesia Urinalysis • Urinalysis is not indicated except for specific procedures (e.g., prosthesis implantation, urologic procedures) or when urinary tract symptoms are present.

The general policy in humans is to recommend specific tests based on specific indicators of risk for each individual patient, not to routinely screen everybody who is going to undergo anaesthesia.

A recent paper in the Journal of Feline Medicine and Surgery found a relatively high incidence of common problems (dental disease, kidney disease) etc. in cat over 10 years of age, which would support screening for these disorders in this population. However, this was a small study, and the population was different in some significant ways from those in other places (for example having a much higher incidence of FIV infection that is typical in the U.S.), so we must be cautious about generalizing these results.

I think a rational approach in veterinary medicine is to screen those patients which there are reasons to suspect may have relevant abnormalities, such as animals with clinical symptoms, older animals, animals with known pre-existing conditions, etc. In the absence of better evidence, the only firm conclusion we can make is that firm conclusions are probably not justified. Anyone who says that pre-operative screening or annual examinations of young, apparently healthy pets is mandatory and that not doing it is malpractice is expressing only their opinion, not a conclusion based on reliable scientific evidence. And anyone who states that such screening is worthless is also going beyond the evidence.

Decisions about screening tests in veterinary medicine are, like so many decisions in our business, as much about the values and risk tolerance of individual doctors and owners as about what can be demonstrated to be the best practice. The major deficiency at this point seems to me to be a failure of veterinarians to recognize that screening has costs and risks that should be considered as well as benefits. True informed consent requires that we make our clients aware of the concerns that have emerged in human medicine over irrational or indiscriminate use of screening tests, and of the limited evidence to support screening asymptomatic pets. Clients should be helped to make informed decisions which consider both the possible benefits of screening and also the costs and risks for them and their pets.

Posted in General, Science-Based Veterinary Medicine | 19 Comments

Evidence-Based Medicine in Song

Posted on March 12, 2013 by skeptvet

Posted in Humor | Leave a comment

Nativis Voyager–A “Revolutionary” New Cancer Therapy for Dogs?

Posted on March 5, 2013 by skeptvet

The Nobel Disease is a well-known tongue-in-cheek reference to the apparent tendency of Nobel laureates, who have obviously made substantial legitimate contributions to scientific knowledge, to develop strong irrational attachments to questionable theories or outright pseudoscience in their later years. The MD Disease is a variant strain in which ordinary doctors with real medical training and skills become champions of scientifically unsound theories or practices. All of this, of course, is just a way of pointing out why the argument from authority is a fallacy. Smart, educated, well-respected individuals, even with the best of intentions, are not reliably less susceptible to bias, cognitive dissonance, confirmation bias, or any of the mental quirks that lead us to passionately commit to dubious, even ridiculous ideas than the rest of us. The status or personal characteristics of a believer in any given idea is not a useful form of evidence in favor of the truth of that idea.

This phenomenon came to mind earlier this week when I was asked to look into a technique being promoted as a possible veterinary cancer therapy, the Nativis Voyager system, which is apparently the focus of a clinical trial, and some pretty optimistic promotion, by the accomplished and well-respected veterinary oncologist Dr. Greg Ogilvie.

It is difficult to find much information about this product, but it manifests many of the warning signs of pseudoscience. In particular, it is referred to by the company and Dr. Ogilvie as “revolutionary” and “ground breaking,” despite the lack of any substantive evidence to support this claim. And the emphasis of the research seems not so much to find out if the technology works but to find out how well and for which types of cancer: “Voyager is just beginning its voyage as we are beginning the process of identifying the cancers its most effective to treat. It seems to have a broad spectrum of efficacy while being quite safe.”

In a promotional Youtube video for Voyager, anecdotes purportedly showing dramatic improvements are presented, and claims are even made to suggest some patients might have experience complete remissions or a cure. I personally do not feel that contributing to promotional marketing videos for the company while conducting a supposedly objective, scientific clinical trial of that company’s product is appropriate. And the claims made are largely meaningless if they are founded solely on anecdotes, which are an unreliable guide to the safety and effectiveness of medical therapies for many reasons.

The plausibility of this device is not enhanced by the proposed mechanism described in the patent application submitted by Nativis. It is full of pseudoscientific nonsense such as this:

An aqueous anti-tumor composition produced by treating an aqueous medium free of paclitaxel, a paclitaxel analog, or other cancer-cell inhibitory compound with a low-frequency, time-domain signal derived from paclitaxel or an analog thereof, until the aqueous medium acquires a detectable paclitaxel activity, as evidenced by the ability of the composition (i) to inhibit growth of human glioblastoma cells when the composition is added to the cells in culture, over a 24 hour culture period, under standard culture conditions, and/or (si), to inhibit growth of a paclitaxel-responsive tumor when administered to a subject having such a tumor.

This appears to be a claim that one can somehow digitally record the curative properties of chemotherapy drugs in solution and then play them back to water, thus transforming the water into a therapeutic substance with none of the unwanted effects of the cancer drugs. Others have investigated such claims from this company and found more direct statements of this highly speculative and implausible idea:

Nativis has developed and patented a breakthrough technology that captures the unique photon field (signal) of active pharmaceutical ingredients (API), or drugs. . .Every drug molecule in a solution is surrounded by a photon field that contains information unique to the molecule. With Nativis’ technology, the photon field, or “drug signal” can be recorded and then replicated for medical treatment. Nativis has proven in preliminary trials that the drug signal – or photonic signature – mimics the original chemical molecule and can unlock the same biological processes as the original to treat diseases, such as brain tumors. With the technology, the drug signal can be reproduced rapidly and flawlessly, each time containing all relevant biochemical information encoded into the new therapeutic signal to drive a biologic reaction. . .

If this sounds vaguely familiar, that’ because it bears an uncanny resemblance to the theories of some homeopaths that the magical healing energy of homeopathic remedies can be digitally recorded and transmitted by telephone or other electronic media. And by an astounding coincidence (or perhaps not?), at least one of the patent holders and key figures at Nativis has previous professional connections with Luc Montagnier and Jacques Benveniste.

Dr. Montagnier is one of the classic examples of Nobel Disease, a co-discoverer of HIV who later became a proponent of homeopathy in both traditional and digital forms. And of course Dr. Benveniste was the author of a famous study in the journal Nature which appeared to show a real biological effect of a homeopathic solution on cells in culture. This effect, however, was later demonstrated to be an illusion due to improper blinding of study personnel, and decades of attempts to replicate it have proven unsuccessful.

Nativis has previously announced a revolutionary new cancer therapy and supporting research evidence which have, in the three years since, not emerged and which are no longer mentioned on the company web site, now devoted to Voyager. A history of claiming revolutionary breakthroughs without published scientific evidence to support them, followed by closing up shop, moving to a new state, and setting up an entirely new product based on almost the same unproven theories, this time for the veterinary rather than human market, is not the behavior of a company I would trust. Certainly, it is not a sound basis for a respected veterinary oncologist to promote the product and make rather strong, optimistic claims about its benefits, raising the hopes of pet owners and using scare resources in the always struggling domain of veterinary oncology research.

Despite his well-earned status in veterinary medicine, Dr. Ogilvie has shown sympathy towards implausible practices in the past. He has been a regular lecturer, and even the Keynote Speaker, at the annual conference of the American Holistic Veterinary Medical Association (AHVMA). This is the same organization that has encouraged and promoted many ridiculous practices at its annual meetings and which recently mounted a major effort to defend homeopathy as a legitimate and scientific therapy. He is also on the advisory board of a “holistic” supplement company along with many of the most prominent spokespeople for homeopathy, so-called Traditional Chinese Medicine, and other alternative veterinary practices. This might explain why, despite his intelligence and unimpeachable credentials as an oncologist, he seems willing to jump on such a ramshackle bandwagon as the Nativis Voyager system.

Of course, the proof of the pudding is in the eating. If convincing and replicable clinical trial evidence eventually emerges showing a significant therapeutic effect for the Voyager, I will be thrilled to have a new and better cancer therapy to offer. If, as I expect is more likely, such evidence never emerges, and this “revolutionary” product goes the way of Dr. Sanden’s Electric Belt, I will be disappointed; both because of the failed promise of a better treatment for my patients and also because of the damage to the credibility of a brilliant veterinarian whose guidance I have often followed in my career.

Posted in Miscellaneous CAVM | 22 Comments

Book Review: Bad Pharma by Dr. Ben Goldacre

Posted on February 20, 2013 by skeptvet

Introduction
Most of the articles I write concern unconventional or alternative therapies. The primary reason for this is that the overwhelming majority of the information available to pet owners about such therapies comes from practitioners and true believers, often with a commercial interest in these therapies. People deserve an independent, skeptical, science-based perspective they can consider when deciding what’s best for their pets, and since there are almost none of these, I have done what I can to provide one.

One of the more superficially reasonable objections to this focus on alternative therapies is that there are many problems with the evidence concerning conventional medicine as well, and there is a need for skeptical and science-based evaluation of all our practices. This is true, and I do engage in such critical appraisal in my daily work, through organizations I belong to, such as the Evidence-Based Veterinary Medicine Association, and sometimes here in this blog. The pharmaceutical reps that come to our practice are no happier to see me than are the chiropractors!

However, the existence of unsolved problems in science-based medicine does not reduce at all the need for critical evaluation of alternative therapies. The limitations of the evidence for conventional practices does not make the implausible plausible, the unproven proven, or the outright ridiculous reasonable. To suggest that no one should critique alternative medicine without giving equal time to criticism of conventional therapies is a fallacy (tu quoque) and a distraction from the weaknesses of the claims made for alternative therapies.

The other problem with the “glass houses” argument is that there is, in fact, much criticism of conventional, science-based medicine coming from within mainstream medicine. Plenty of people are working on identifying and fixing many of the problems with the development and delivery of science-based medical care, and while perfection is nowhere in sight, it is possible to track improvement over time (albeit often frustratingly long periods of time). The folks promoting alternative medicine seem, at least in public, far less willing to criticize their own colleagues or take on the dramatic and egregious problems with claims not based on good evidence within their fields.

A shining example of critics of alternative medicine and proponents of science-based medicine taking on the task of setting our own house in order is the recently published Bad Pharma by Ben Goldacre (recently published here in the U.S., at least, though it’s been out in the U.K. for a while).

Dr. Goldacre, a British academic physician, has been a long-time critic of nonsense of all kinds in all areas of medicine. He is a prominent, articulate skeptic who has given much grief to promoters of homeopathy and other forms of alternative medicine through his well-researched and well-reasoned columns in the Guardian newspaper, collected in his previous book Bad Science. But he has never spared the pharmaceutical industry, government regulators, or his colleagues in journalism and medicine from direct criticism when they fail to meet his standards for a scientific, evidence-based approach to medicine.

This book provides a set of cogent arguments and a good collection of empirical evidence to illustrate the deep flaws in our system for establishing safety and efficacy of pharmaceutical therapies and for making clinical decisions about the best use of these medicines. It is not without flaws, which I will discuss, but overall it is a readable and important contribution to the betterment of science-based medicine, and I encourage everyone involved in any aspect of medicine, as a researcher, doctor, or as a patient, to read Bad Pharma. And since we are all patients at some point in our lives, that means everyone!

The book has been reviewed in fair detail at Science-Based Medicine, so I will focus on making some general comments about the strengths and weaknesses of the case Dr. Goldacre makes.

Strengths & Weaknesses
Bad Data
The strongest part of the book by far is the analysis of how incomplete and potentially misleading the evidence is from clinical trials sponsored and conducted by the pharmaceutical industry. Dr. Goldacre does a brilliant job of illustrating how a systematic, comprehensive, devastatingly effective system for misleading regulators, doctors, and the public about pharmaceutical therapies can exist without widespread, deliberate lying or an omnipotent conspiracy involving industry, government, and the medical professions. In the sneaky way so common to corporations generally, the pharmaceutical industry manages to rig the game through small, often seemingly innocent steps that aggregate themselves into a deeply flawed system without much if any need for shadowy conspiracies and puppet masters.

Oh, there’s undoubtedly individual malfeasance involved, of course. Much of what we know about how the system works comes from internal documents made available as part of legal cases against the big drug companies. However, the vast majority of individuals working in this industry are smart, well-intentioned, honest people trying to develop new and better medicines. The importance of recognizing this lies in understanding that the way to fix the problems of this industry involve much more than simply finding and cleaning out the bad apples. The system for generating and distributing research information about drugs has to be designed to compensate for the often innocent and unconscious biases that tilt the findings in a direction favorable to the companies even when there is no deliberate program to do so.

Dr. Goldacre does offer some reasonable proposals for achieving this, though he also illustrates how previous reasonable proposals have failed, through lack of enforcement, lack of interest, or unexpected ways the system can adapt to achieve the same misdirection in new ways when some problems are fixed. Overall, Dr. Goldacre does such an effective job illustrating the problem, it is hard to come away with much hope that it can be fixed, despite his assertions that he believes it can. One of the weaknesses of the book is that his efforts at driving home the complexity and severity of the problem are often more successful and convincing than his proposals to solve it.

Drug Approval
Bad Pharma also reviews the process by which drugs are developed and approved for human use. Since this is a lengthy and complex process, Dr. Goldacre necessarily presents a brief, simplified version with a frame intended to illustrate primarily the opportunities for trouble and erroneous or unreliable data. He does not, perhaps, offer an entirely fair view of the difficulties both inherent in the process for biological reasons and imposed by the commercial nature of the endeavor and the often irrational and inconsistent regulatory conditions under which it operates. There are many reasons why developing safe and effective medicines is tremendously challenging apart from the production of misleading and unreliable research data. However, the book was not intended as a “fair and balanced” review of the process but as an expose of its flaws and a call to action. In keeping with Dr. Goldacre’s own suggestion later in the book, it is appropriate to view this section, and the others, with this agenda in mind. The specific points he does make are, as best I can tell, accurate.

Bad Regulation
Dr. Goldacre also spends a fair bit of time discussing the gross inadequacies of the system for regulating the pharmaceutical industry. He presents something of a conflicted view, both making a compelling case for the failure of government regulation and yet repeatedly suggesting regulation as a solution to many of the problems in the industry. I appreciate this conflict as I tend to share it. I have written often about the regulation of medicine in general (e.g. 1,2,3,4) and why I feel it is frequently inadequate at protecting patients from even the most egregious pseudoscience and quackery (e.g. 5).

However, I also believe that consumer choice and market mechanisms cannot do the job, and that the solution to ineffective regulation is more and better regulation properly enforced. Again, I think Dr. Goldacre lays out the problem clearly and effectively, but it does somewhat undermine his own case when he suggests further regulation as an important part of dealing with the problems he identifies. It is important to recognize that the quality of medicine, and the usefulness of research evidence, was far worse in the era of “medical anarchism” before widespread regulation, and it continues to be far worse today in unregulated or under-regulated domains such as dietary supplements and herbal remedies than it is in the domain of pharmaceuticals. The legitimate failings Dr. Goldacre identifies are important and urgent problems, but not a reason to abandon ship or forget the value we get from the regulatory mechanisms we have.

Bad Studies
As an epidemiologist-in-training, one of my favorite parts of the book were the sections dealing with ways in which clinical trials can be designed to generate misleading findings favorable to the sponsor. The whole point of clinical trials, of course, is to compensate for chance, bias, confounding, and sources of error that lead us so easily astray in our day-to-day evaluation of how the world works. The success of science has been due primarily to this ability to compensate for the collective and several weaknesses of individual scientists.

However, the system is not perfect, and there is good reason to believe residual bias and improper design and execution bedevil much medical research. This is part of what makes the processes of evidence-based medicine, which critically evaluate all the research and draw conclusions based on the entire body of evidence in a given area, so crucial.

Dr. Goldacre gives many specific examples of how trial results can be shaped to be misleading, from the selection of unrepresentative patient populations to inappropriate or shifting outcome measures, inappropriate controls, inadequate randomization and blinding, early termination, and dodgy statistics. All of these are flaws which can be easily identified if the full details of the process are publically available from start to finish, which is one of the most important recommendations made in the book for dealing with the problems identified.

Marketing
Finally, Dr. Godlacre addresses the abuses and excesses of the pharmaceutical industry marketing machine, which exists entirely to increase the revenue generated by the industry’s products and yet which masquerades as a system for disseminating useful information to doctors, patients, and politicians. This subject has been covered extensively by others, so there is not much new in this review of the problem.

I also think this section contains some of the weakest parts of Dr. Goldacre’s argument. When he discusses potential conflict of interest, he acknowledges that it is difficult to argue that anyone doesn’t have one. Ideological or philosophical biases and personal relationships can shape our conclusions as much as financial incentives, so no one can claim to have no bias at all. That is, after all, why we need the methodology of science.

But there likely is a reasonable, if somewhat arbitrary point, at which one can distinguish between the ordinary bias that comes from having a point of view and recessive, inappropriate corporate influence on doctors and political decision makers. Dr. Goldacre’s primary suggestion for dealing with conflicts of interests is extreme transparency, suggesting, for example, that any and all affiliations with industry a doctor may have be disclosed in the waiting room of their office or on the Internet. Dr. Goldacre seems to feel that this disclosure will convey the impression to the public of possible conflict of interest and that subsequent public pressure will discourage inappropriate relationships between doctors and industry.

My concern with this line of reasoning is that it feeds all kinds of cognitive bad habits that can lead us to judge people’s claims inaccurately and inappropriately. If any association with industry is seen as suggestive of possible bias, and if almost everyone has some such association, however tenuous, than disclosing these alone will simply convey the impression that all doctors, and medicine as a whole, is merely a tool of the pharmaceutical industry and that recommendations made by our doctors can be dismissed on this basis alone, regardless of the evidence for or against them. I realize, of course, most people are unlikely to be this unreasonable, but unfortunately in the context of this blog I meet a fair number of people who are not and who are looking for any opportunity to play the “pharma shill” card to dismiss science-based medicine in favor of some alternative that is even less evidence-based and reliable.

I do support disclosure of commercial interests that might plausibly introduce bias into research or clinical practice, but I think it would be appropriate to make some reasonable distinctions about what kind of relationships matter or are clearly inappropriate and what kind are less concerning. And ultimately, we cannot eliminate individual bias, so our efforts are likely to be most productive if we focus on ensuring transparent and effective research methods to control for it.

In any case, there is no question that the shift in public political values and priorities, especially in the U.S., has led to a situation in which the lion’s share of medical research is supported by commercial interests rather than government. This has had the consequence of raising the threat financial bias poses to the integrity of research data. And the marketing mechanisms employed by the pharmaceutical industry are often a paragon of cynical, blindly self-interested manipulation of opinion not conducive to the best interests of patients.

Bottom Line
Bad Pharma is a compelling and important exposé of the well-known but still unresolved problems with the influence of pharmaceutical companies on the generation and distribution of research evidence concerning drug therapies. It skillfully and convincingly identifies many specific problems. It also offers many reasonable and practical suggestions for improving the situation, though the strength of the solutions offered is noticeably weaker than the strength of the case made for the problems themselves, leaving one struggling with a bit of pessimism about the chances of reforming the system in significant and effective ways.

In addition to illustrating the problem and discussing solutions, Dr. Goldacre has partnered with the British Medical Journal, The Centre for Evidence-Based Medicine, Sense About Science, and the James Lind Initiative to form the All Trials Campaign. This effort is focused primarily on pressure the pharmaceutical industry, governments, medical professionals, researchers, and patient organizations to take steps to ensure all research data related to pharmaceuticals is freely, efficiently and widely available so that the evidence-based analysis necessary to guide medical practice has access to the evidence it needs to draw correct conclusions. I encourage everyone interested in improving the state of medical science and healthcare to support this initiative and to read Dr. Goldacre’s book.

Posted in Book Reviews | 3 Comments

Benefits and Risks of Neutering, an Evidence Update: Study Investigates Effects of Neutering in Golden Retreivers

Posted on February 17, 2013 by skeptvet

Given that I recently presented a couple of evidence-updates on the subject the health effects of neutering, the timing was excellent for the release last week of a new research study looking at the same issue.

Torres de la Riva G, Hart BL, Farver TB, Oberbauer AM, Messam LLM, et al. (2013) Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers. PLoS ONE 8(2): e55937. doi:10.1371/journal.pone.0055937

This was a retrospective cohort study in which records were searched to identify Golden Retrievers who had been patients at the UC Davis veterinary school, were between 12 months and 8 years of age, and who could be classified as having been neutered “early” (before 12 months of age), “late” (after 12 months of age), or not at all. The occurrence of a number of diseases common in Golden Retrievers was then evaluated to see if it differed between dogs in these three categories. There are several reasons to be cautious in how we interpret the results of this study, but let’s start by looking at what those results were.

The authors looked at the occurrence of hip dysplasia (HD), elbow dysplasia (ED), cranial cruciate ligament rupture (CCL), and a number of cancers com including lymphosarcoma (LSA), hemangiosarcoma (HSA), mast cell tumor (MCT), osteosarcoma (OSA) and mammary cancer (MC). The figures below illustrate the relative occurrence of some of these diseases in males and females by neuter status (the diseases not shown did not occur often enough to be included in the analyses).

Figure 1. Percentages and number of cases over the total sample size for each neutering status group; intact and neutered early or late for male Golden Retrievers (1–8 years old) diagnosed with hip dysplasia (HD), cranial cruciate ligament tear (CCL), lymphosarcoma (LSA), hemangiosarcoma (HSA), and/or mast cell tumor (MCT) at the Veterinary Medical Teaching Hospital of the University of California, Davis, from 2000–2009.

For HD and LSA, the differences between early-neutered and intact or late-neutered groups were statistically significant (K-M), as were differences for CCL between intact and early-neutered groups.

Figure 2. Percentages and number of cases over the total sample size for each neutering status group; intact and neutered early or late for female Golden Retrievers (1–8 years old) diagnosed with hip dysplasia (HD), cranial cruciate ligament tear (CCL), lymphosarcoma (LSA), hemangiosarcoma (HSA), and/or mast cell tumor (MCT) at the Veterinary Medical Teaching Hospital of the University of California, Davis, from 2000–2009.

For CCL the difference between intact and early-neutered was statistically significant (K-M). For HSA, the differences between early and late-neutered and intact and late-neutered groups were statistically significant (RR), as were differences for MCT between early and late-neutered groups. A similar statistical comparison for late neutering and intact groups was not possible for MCT because there were 0 cases in the intact group.

doi:10.1371/journal.pone.0055937.g002

These results suggest that there is a complex and inconsistent pattern of associations between neuter status and these diseases. In general, there was a tendency for neutered animals to have higher rates of these diseases than intact animals and for early neutered animals to have higher rates than late neutered animals. However, there are many cases in which differences were not statistically significant or the difference was significant in one sex but not the other, and a few in which the direction of the difference was opposite that expected (for example with HAS occurring more often in late-neutered females than either intact or early neutered females).

The difficulty lies in knowing what these results mean in terms of predicting the risks for individual pets and making decisions about neutering in general. The natural tendency will be to look at these data and conclude that not neutering, or neutering after 12 months of age, is safer than the common current practice of neutering most animals before 12 months. However, this is not a conclusion we can reliably draw from these data.

To begin with, this is a group of dogs that are, in many ways, very different from most dogs neutered by veterinarians. Apart from only representing one breed, and a breed known to have higher rates of the diseases studied than most other breeds, the subjects were patients at a university veterinary hospital. In general, only the sickest animals with the most unusual or serious diseases are seen at universities. Most healthy animals or those with typical illness are seen at general veterinary practices. So it is uncertain if neutering will have the same effects as in this study on dogs of other breeds or those healthy enough to have never seen the inside of a university hospital.

The population also contained small numbers of intact and “late” neutered dogs. This makes it more likely that small, random differences in the health of individual dogs in the study group could alter the apparent effects of neutering on health. And the authors chose to limit the study population to dogs between 12 months and 8 years of age. Quite a few Golden Retrievers live past 8 years, and the rates of cancer generally go up dramatically with age. If the proportion of these diseases among intact and neutered animals over 8 years old are at all different from those in dogs under 8, then the direction and statistical significance of the differences between groups seen in this study could easily be altered.

And it’s important to consider the absolute risk and benefit numbers when making decisions about whether to neuter. If, in fact, neutering is strongly protective against a common cancer (as it is thought to be for mammary cancer) but also slightly increases the risk of a rare cancer, it may still make sense to neuter early depending on the unique situation of an individual patient.

Finally, two of the major diseases against which neutering is thought to be protective in females, uterine infection and mammary cancer, did not occur often enough to be included in the analysis. This may be because relatively few of the dogs were intact or because of the age cutoff. Obviously, if there really is a protective effect of neutering on these diseases that didn’t show up in this study, that might influence the interpretation of the results.

Overall, this is a useful piece of research adding to the information we have about the pros and cons of neutering and the possible role of age in the effect of neutering on disease. It should be over-interpreted as the final word by itself, but it should be incorporated into a broad analysis of all the available evidence.

As it stands, there is reason to believe early neutering has significant benefits in females, though as the recent systematic reviews pointed out the evidence behind this belief is not strong. There is also reason to be concerned about possible risks, though the evidence for this is also not robust yet. On balance, one can make a reasonable case on both sides, and the risk profile for individual dogs, as well as larger issues such as the problems associated with unwanted reproduction. Anyone who says there is an absolute and universal right answer concerning if and when to neuter female dogs is exaggerating by quite a bit.

For males, I believe the evidence of benefits from neutering, especially before 12 months of age, is not compelling, and I don’t see a strong reason to neuter earlier in the case of owned dogs with owners willing to commit to preventing roaming and unwanted reproduction and in the absence of intolerable interdog aggression. For large breeds in particular, delaying neutering of males seems reasonable, though we very much need better evidence to have confidence in such a recommendation. It is encouraging that more attention is now being paid to the complexities of neutering and the risks and benefits associated with it, and I am optimistic that this will lead us to more reliable guidelines in the future.

Posted in Science-Based Veterinary Medicine | 12 Comments

The Myth of Antioxidants?

Posted on February 12, 2013 by skeptvet

I have written often about the popular notion that vitamins, dietary supplements, herbs, and other things which can be identified as “antioxidants” based on in vitro laboratory studies must automatically be good for our pets. This sort of simplistic reasoning is rarely justified in biology, and there is ample reason to doubt the hype that free radicals and oxidation are always bad and that antioxidants are always good.

In terms of specific supplements, there is large-scale clinical research evidence showing that even essential antioxidant vitamins, such as Vitamin E and Vitamin C, are not only not beneficial in excess but can increase the risk of cancer, heart disease, and other serious ailments and interfere with some medical treatments, such as chemotherapy. The common alternative medicine mantra that such supplements prevent cancer and other diseases, or help “boosting the immune system” in patients with serious illness, is inaccurate and potentially dangerous.

A recent review in Scientific American magazine does a nice job of summarizing the growing research evidence of the last decade showing that the theory of oxidative damage as a primary driver of aging and disease is deeply flawed, and that antioxidant supplements (as opposed to fruits and vegetables in their whole form) can often do more harm than good.

Moyer, M.W. The Myth of antioxidants: The hallowed notion that oxidative damage causes aging and that vitamins might preserve our youth is now in doubt. Scientific American. February, 2013. 64-67.

Though intended for the general public, and thus not a systematic review, this article does a good job of identifying several areas in which theories about the role of free radicals and antioxidant appears to have failed to hold up. The first is the notion that oxidative damage is a key component of aging and that reducing oxidation and supplementing antioxidant should lengthen life. The article cites a number of laboratory studies in invertebrates and mammals showing that animals genetically engineered to have reduced activity of natural antioxidant systems do, in fact, have increases in free radicals. However, these animals live longer than animals with better antioxidant function! And supplementing these subjects with antioxidants reduces their life expectancy to that of animals with normal anti-oxidative functions.

The author also reviews some of the early studies produced by the first proponents of the oxidative damage theory, and points out that attempts to replicate these have usually failed. There are even studies showing that application of an herbicide which increases free radical production can increase lifespan in some laboratory species, and again antioxidant supplementation eliminates this increase in life expectancy.

More nuanced theories suggest that, as is usually the case, the truth is complex and depends on context and many factors. There are undoubtedly situations in which free radicals and oxidative damage are harmful. But there may also be situations in which increases in free radicals may be beneficial. Such oxidative compounds increase as a consequence of exercise, for example, and antioxidant vitamins appear in some research to attenuate the benefits of exercise. And oxidative damage is one mechanism by which the immune system and some medicines destroy infectious organisms and cancer cells. Antioxidant that interfere with these beneficial activities can actually cause harm.

There is much work yet to be done to refine our understanding of the positive and negative effects of oxidation and antioxidants, but one thing is clear. Simplistic notions of antioxidant supplements as automatically beneficial are nonsense and not a sound basis on which to recommend supplements, herbal remedies, or other preventative or therapeutic products.

Posted in Herbs and Supplements, Science-Based Veterinary Medicine | 10 Comments

Benefits and Risks of Neutering, an Evidence Update: Neutering and Mammary Cancer in Female Dogs

Posted on February 8, 2013 by skeptvet

This is another in my series of evidence updates on the risks and benefits of neutering in dogs and cats. I will be updating the evidence and conclusions of my original 2010 review based on a series of systematic reviews being produced by a research group in the UK. The first such update concerned the effect of neutering and age at neutering on urinary incontinence in female dogs. This update concerns one of the most important reasons to considering neutering female dogs: mammary cancer.

Beauvais W, Cardwell JM, Brodbelt DC. The effect of neutering on the risk of mammary tumours in dogs–a systematic review.J Small Anim Pract. 2012 Jun;53(6):314-22.

In my 2010 review, I found evidence suggesting that mammary cancer is very common in intact female dogs, that it is malignant about half the time, and that neutering dramatically reduces the risk of this disease. I also found evidence suggesting that neutering is most effective in preventing mammary cancer if performed before the first heat, and that the benefit disappears after the third estrus cycle. This is a major reason why I still recommend neutering young female dogs.

The UK group found only 4 research reports that addressed the question of the impact of neutering on mammary cancer risk and that met the minimum quality criteria for review. One of these also addressed the issue of whether age at neutering was associated with mammary cancer risk. They reported the following results:

All studies had significant methodological flaws, and none provided information that could be confidently generalized to the general dog population.
One study found a strong protective effect of neutering. Another found some protective effects but these were inconsistent. The remaining two studies found no association between neutering and mammary cancer risk.
The one study that evaluate age at neutering found a significant decrease in the protective benefits of neutering with each of the first three heats, and no benefit after the third heat.

Once again, the general conclusions are consistent with the current consensus, that neutering young female dogs likely has a meaningful beneficial effect on reducing the risk of mammary cancer later in life. However, the existing evidence is extremely weak, and this conclusion has to be viewed as tentative. While current evidence does not justify a change in the common practice of recommending neutering to prevent mammary cancer, we cannot view our current conclusion with any great confidence, and we desperately need more and better quality research to determine if the current evidence is correct or if a significant change in our recommendations is called for.

As always, the decision to neuter must be based on the entirety of the known risks and benefits, with a clear understanding of the uncertainty involved, as well as on the unique circumstances of each individual. The value of this review is not so much in answering our questions about the subject, which it cannot do, but in making it clear what the strengths and weaknesses are in the evidence behind our current recommendations and in guiding us in the development of better evidence that will permit more confident conclusions.

Posted in Science-Based Veterinary Medicine | 11 Comments

Benefits and Risks of Neutering, an Evidence Update: Neutering and Urinary Incontinence in Female Dogs

Posted on February 8, 2013 by skeptvet

A couple of years ago, I wrote a review of the risks and benefits of neutering. This handout, originally intended for clients, was also turned into a journal article for veterinarians:

Evaluating the benefits and risks of neutering dogs and cats CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources 2010 5, No. 045

This was a narrative review, not a systematic review. This means that I found as many research reports as possible related to the subject and informally evaluated their conclusions. I did not conduct a formal appraisal of the level and quality of the research evidence according to predetermined and standardized criteria, as would be done in a systematic review.

There are pros and cons to each format. A narrative review is more likely to reach pragmatic conclusions based on the existing evidence, whereas a systematic review is more likely to end with no useful conclusion if the quality of the evidence examined is less that perfect, which it almost always is. However, a systematic review is likely to be more thorough and provides a better picture of how strong the existing evidence is so that it is possible to gauge how much confidence we ought to have in the conclusions we base on it.

As a practicing clinician, I need to make practical decisions even when the evidence isn’t perfect, so a narrative review was more suited to my goals. However, as a strong supporter of the practice of evidence-based veterinary medicine, I believe systematic reviews and a clear understanding of the limitations of the available evidence on specific subjects is critical to making fully informed decisions. So I am thrilled to see that a research group in the U.K. has begun producing a series of systematic reviews of the evidence concerning the risks and benefits of neutering in dogs. I intend to evaluate these reviews as they appear to help update and appraise the evidence on this important subject and provide a bit of context for veterinarians and pet owners trying to make practical decisions about neutering. The first subject reviewed was the potential effect of neutering on the risk of urinary incontinence.

Beauvais W, Cardwell JM, Brodbelt DC.The effect of neutering on the risk of urinary incontinence in bitches – a systematic review.J Small Anim Pract. 2012 Apr;53(4):198-204.

In my 2010 narrative review, I was only able to report research suggesting urinary incontinence was common in spayed female dogs and that the research was conflicting on whether incontinence was more common in dogs spayed at younger ages. I did not identify specific research comparing the occurrence of incontinence in intact and spayed females.

The UK group identified only one research study evaluating the relative risk of incontinence in neutered and intact dogs, and three studies evaluating the effect of age at neutering on incontinence risk. The authors concluded the following:

1. All the evidence was weak, with a significant risk of error

2. The one study that evaluated risk of incontinence with neutering found that neutering significantly increased the risk of incontinence.

3. Two of the three studies found no association between age at neutering and incontinence and one found that incontinence was more likely the younger dogs were when neutered.

So the conclusions are consistent with the current consensus, that neutering female dogs does increase the risk of urinary incontinence and that age at neutering probably does not affect this risk significantly. There is, of course, significant uncertainty because the evidence is quite weak. That does not mean, however, we cannot reach a conclusion or make recommendations. If this were the case, we would almost never be able to decide anything in medicine since the evidence is often imperfect. It simply means that we have to acknowledge the uncertainty and recognize that our conclusions are provisional and might need to change as new evidence emerges.

Any decision about neutering should not, of course, be based solely on this single issue. Urinary incontinence, while inconvenient, is a relatively minor and highly treatable clinical problem. And there are a large number of other risks, benefits, and personal considerations involved in making a decision about neutering. The important thing is that we make informed decisions and that we understand the strengths and weaknesses in the available evidence. The reviews produced by this group will be invaluable in facilitating this.

Posted in Science-Based Veterinary Medicine | 1 Comment

Measuring Arthritis Pain in Dogs: Are Owner Surveys as Good as Force Plate Analysis?

Posted on February 4, 2013 by skeptvet

I have written about a wide variety of conventional and alternative therapies for arthritis pain in dogs. A recurring issue in evaluating these therapies is how we know whether or not interventions designed to reduce pain in animals are effective. While I do not think dogs have beliefs or expectations about their treatment, and so do not experience the kind of direct placebo effect people can, they can manifest differences in both the objective features of their illness and in the symptoms they exhibit when given placebo therapies, due to a variety of effects others have described (e.g. classical conditioning, human interaction, etc.). The indirect placebo effect of a therapy on the vets and owners involved in studying a pain control treatment for dogs are well-documented, and these frequently lead us to believe such therapies are effective when they aren’t. So finding a reliable, repeatable, and accurate measure of the effect of a pain medication is critical.

The gold standard for testing arthritis medications in dogs is force plate analysis. This tool involves having a dog walk across a plate that records the amount of weight carried on each limb. As pain is decreased with treatment, lameness improves and the amount of weight the dog can carry on the affected limb increases. This is a technically challenging tool, but the most accurate and objective way we have of knowing if we have successfully diminished pain in a dog’s limb.

A subjective measure of some kind is often used in arthritis treatment studies instead of force plate analysis because such tools are easier and less expensive to use. With proper blinding and controls, subjective evaluations by owners and veterinarians can have some value in measuring response to pain treatment. However, the results of such evaluations are often inconsistent, and the risk of uncontrolled placebo effects is high.

A new study has attempted to validate a subjective owner rating tool by comparing the results of this survey to force plate analysis in dogs with newly diagnosed arthritis given a NSAID or a placebo.

Brown DC, Boston RC, Farrar JT.Comparison of force plate gait analysis and owner assessment of pain using the canine brief pain inventory in dogs with osteoarthritis. J Vet Intern Med. 2013 Jan;27(1):22-30.

The dogs in this study were assessed by force plate gait analysis the first day, and the owners completed a previous validated questionnaire about pain and the degree to which it interfered with their pets’ activities. The dogs were then randomly assigned to either a placebo or NSAID treatment and re-assessed in 2 weeks.

As expected, the dogs on NSAID therapy showed a significantly greater increase in the weight placed on their arthritic limbs than those placed on the placebo. This objectively showed that the medication improved their lameness, and presumably their pain. The two measures of effect in the client questionnaire also showed significant improvement in dogs on NSAID compared to dogs taking placebo. This would seem to show that the questionnaire also accurately identified the improvement in pain on the medication..

However, the authors also found that there was no correlation or concordance between the survey measures and the force plate analysis. In other words, while overall the survey scores changed in the expected way, the survey scores and force plate analysis measurements for individual dogs didn’t seem to be related or to change together.

What does this mean? Well, the authors argue that both the survey and force plate analysis are measuring real improvements in pain, but the force plate specifically measures the change in lameness associated with treating pain while owners are measuring more general signs of comfort and normal activity at home. This is certainly a plausible explanation, but it doesn’t entirely make sense.

If the drug reduces pain, and pain is causing the lameness, then as pain decreases the lameness should decrease. The force plate results show that this is what is happening. However, if the surveys are also measuring accurately the reduction in pain, even if they are not measuring lameness, then the decrease in pain and the improvement in lameness should occur together and the two measures should correlate.

Think of it this way. Let’s say we want to measure the effect of a drug in reducing nausea and vomiting. If we count the number of episodes of vomiting, and the drug clearly reduces how often a person throws up, then that is an objective, though indirect, measure of nausea (analogous to force late analysis evaluating pain by measuring lameness). And if we ask people about their nausea, and if they say they are less nauseated when taking the drug, that is another way to measure nausea and the effect of the drug (analogous to asking clients about their dogs’ pain). But if both tests are measuring the same thing, then the results should correlate. People who say they feel less nauseated should vomit less than people who say they don’t feel any better.

But what happens if we give the drug and on average the group reports they feel less nauseated and overall they vomit less, but the individual responses on the survey don’t match the frequency of vomiting? People who say the feel better might or might not vomit less. And people might show less vomiting even when they say they don’t feel any less nauseated. Are the survey and the frequency of vomiting both measuring nausea? And which is more important? Do we primarily want people to report feeling better but still vomit just as much, in which case the survey might an appropriate tool? Or is it more important to reduce the amount of vomiting even if some people who vomit less say they don’t feel better?

In the case of arthritis pain in dogs, it is difficult to picture a situation in which reducing the signs of pain perceptible by the owner is more important than reducing the lameness caused by the pain. This raises the question not only of what the owner survey is actually measuring but also the question of when would it be an appropriate tool to use to measure the efficacy of an analgesic therapy. If animal owners report their pets have less pain but we don’t have an objective measure such as force plate analysis, it seems likely that the intervention is changing something about the dogs’ behavior which the owners are detecting, but it isn’t clear that something is pain.

Posted in Science-Based Veterinary Medicine | 4 Comments

Repeat After Me: “Dogs are not Wolves”

Posted on January 25, 2013 by skeptvet

It should be obvious that there is a difference between acknowledging domestic dogs evolved from wolves (which is a widely accepted theory with strong supporting evidence) and saying that dogs essentially are wolves (which is nonsense). Try to picture a pack of pugs or Bichon Frise brining down and savaging an elk, and the impact of artificial selection ought to be quite clear.

Unfortunately, people all too often misconstrue the ancestry of dogs as a justification for extrapolating from what they know (or think they know) about wolves and applying that knowledge to our canine companions. The infamous “alpha roll,” is an example of this. Attempting to establish a healthy, smoothly functioning relationship with your dog by periodically tackling and pinning him or her to the ground, preferably while growling ferociously, is a ludicrous idea that nevertheless managed to gain some popularity at one time on the basis of the argument (grossly oversimplified) that that is how wolves establish stable dominance relationships.

The most prevalent form of this kind of phylogenic fallacy today are some of the canine dietary fads, including raw meat-based or BARF diets, grain-free diets, and so-called “biologically appropriate” feeding. I’ve written about BARF diets, and the fallacious reasoning behind then, before. And I have written numerous times about raw diets and all the reasons why the have no proven benefits and at least some undeniable risks (for example). While the statement that the dietary needs of dogs may be similar to those of wolves in some ways, based on their phylogenetic relationship, is perfectly reasonable, the claim that one can accurately predict the optimal diet for dogs based on what wolves eat in the wild is simply nonsense. The dietary needs of dogs have been shaped by many factors, not least among them their long association with humans, and they need to be worked out through thorough and rigorous scientific research, not speculation and the appeal to nature fallacy.

An example of the kind of research that we need, which also shows in specific and relevant ways that dogs are not wolves, is a recent study reported in the journal Nature:

Erik Axelsson,Abhirami Ratnakumar,Maja-Louise Arendt, Matthew T. Webster,Michele Perloski,Olof Liberg,Jon M. Arnemo,Kerstin Lindblad-Toh^.. The genomic signature of dog domestication reveals adaption t a starch rich diet. Published online January 23, 2013. doi:10.1038/nature11837

The study consisted of a thorough comparison of dog and wolf genomes, identifying a number of differences related to the domestication process. Many of these differences have to do with genes involved in brain development and function, which will hopefully help us to better understand the behavioral differences between dogs and wolves related to domestication. But a significant subset of the genes found to be different between dogs and wolves involve the digestion of starch. Starch was an important energy source for humans at the time of the domestication of the dog, and so dogs adapted to the available food in ways that distinguish them from their more carnivorous ancestors.

Our results show that adaptations that allowed the early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves, constituted a crucial step in early dog domestication…The results presented here demonstrate a striking case of parallel evolution whereby the benefits of coping with an increasingly starch-rich diet during the agricultural revolution caused similar adaptive responses in dog and human.

This genetic information, and the already well-known anatomic differences between dogs and wolves, make it clear that domestication has dramatically altered the structure and function of the dog body. Extrapolating from the natural diet of wolves to the nutritional needs of dogs is not reasonable nor supported by the data, which instead indicates that dogs are more suited to an omnivorous diet. The current fad that identifies carbohydrates in general, and grains in particular, as inappropriate and harmful for dogs is irrational and contrary to the clear evidence that dogs are well-adapted to such food sources.

Posted in Nutrition | 35 Comments