WVC 2016: What You Know that Ain’t Necessarily So

Here is my presentation on the evidence for a few common veterinary practices.

Experienced clinicians often have an enormous knowledge base about the health problems their patients present with and the available diagnostic and therapeutic options. This knowledge is built over time from a variety of sources: basic pathophysiology and clinical information learned in school; practice tips and pearls imparted by professors and speakers at continuing education meetings; review articles and primary research papers in veterinary journals; textbooks; advice from mentors and colleagues in practice; and of course clinical experience with previous cases.

This knowledge base smoothly and efficiently informs the day-to-day activities of clinical practice. When cases with familiar features are seen, the appropriate diagnostic and treatment steps often come to mind automatically, or with minimal prodding. Unlike students and new graduates, experienced clinicians often have little sense of dredging up facts committed to memory and more of a sense of simply knowing things. One of the hallmarks of expertise is that the collating of observations and relevant knowledge into a coherent picture of the problem and a plan become less deliberate and more automatic with time.1

While this process, which is a universal and automatic feature of how the human brain functions, leads to greater efficiency than the explicit, conscious use of algorithms and reference sources employed by less experienced practitioners, it has a number of potential limitations. One problem, for example, is that the knowledge one relies on often can no longer be connected to its original source. We often simply know things without being aware of how we came to know them. This limits our ability to judge the reliability of the source of our knowledge. In fact, such established, automatic knowing often generates a sense of certainty greater than that which accompanies deliberately seeking and finding information.2 We are more likely to trust what we already know, even if we don’t remember where we learned it, than we are to trust what we have just discovered after searching a trustworthy source of information.

There are also a large number of well-characterized cognitive biases and sources of errors inherent in how our brains acquire, process, store, and utilize information that can lead us astray.3 These are more likely to create error when our reasoning is automatic rather than deliberate, as it necessarily must be in an efficient clinical environment that is not devoted primarily to teaching.

One of the major functions of evidence-based veterinary medicine (EBVM) is to provide tools and resources to make the knowledge base we employ more reliable. This includes generating better quality information through research and facilitating the integration of that information into clinical decision making. When the relevant evidence is of high quality, this can add confidence to our decisions.

More commonly, when the evidence has significant limitations, we may end up with less confidence in our knowledge than we would have without an explicit evaluation of the evidence. However, this is not as undesirable an outcome as it may appear. A clear, accurate understanding of the uncertainty associated with a particular practice protects us, and our patients, from the dangers of acting with unjustified confidence. We are more likely to weigh thoughtfully the risks and benefits of action in the context of an individual case when we understand the degree of uncertainty about our ability to predict or manipulate the patient’s condition.

Being clear about the sources of our knowledge, and the appropriate level of confidence to have in them, also aids in fulfilling our duty to provide clients with informed consent. Surveys of veterinary clients have shown that they value truthfulness highly in the information we provide to them, and that they want to be made aware of the uncertainties involved in the treatment of their animals.4-5 Only if we understand the reliability and limitations of the information we employ in making our recommendations can we give clients the knowledge and guidance they need to make informed choices.

The purpose of these lectures is to examine some widespread or long-standing beliefs and practices in small animal medicine and assess their evidentiary foundations. In some cases, this may clearly validate or invalidate these beliefs. In most cases, however, such an exploration will likely not lead to greater certainty but to a clearer understanding of the degree of uncertainty associated with these beliefs. Hopefully, this will be useful in making clinical decisions and in communicating with clients. The exercise may also be useful in illustrating how to make use of the research literature in establishing and maintaining the knowledge base that informs one’s clinical practice.

Some of the topics that will be covered include:

  1. Pheromone therapy for behavioral problems in dogs and cats
  2. Anti-histamines for treatment of atopic dermatitis in dogs
  3. Steroids for anaphylaxis and acute allergic reactions


  1. Benner, P. From novice to expert. Amer J Nursing, 1982; 82(3):402-7.
  2. Burton, R. On Being Certain: Believing You’re Right Even When You’re Not. New York: St. Martin’s Press. 2008
  3. McKenzie, BA. Veterinary clinical decision-making: cognitive biases, external constraints, and strategies for improvement. J Amer Vet Med Assoc. 2014;244(3):271-276.
  4. Mellanby RJ, Crisp J, De Palma G, et al. Perceptions of veterinarians and clients to expressions of clinical uncertainty. J Small Anim Pract 2007;48:26–31.
  5. Stoewen DL, et al.  (2014) Qualitative study of the information expectations of clients accessing oncology care at a tertiary referral center for dogs with life-limiting cancer. J Am Vet Med Assoc. 2014;245(7):773-83.



What Aint So Title

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6 Responses to WVC 2016: What You Know that Ain’t Necessarily So

  1. Art Malernee dvm says:

    “A Cochrane Collaboration meta-study found that routine annual physicals did not measurably reduce the risk of illness or death, and conversely, could lead to over-diagnosis and over-treatment. The authors concluded that routine physicals were unlikely to do more good than harm. ”
    In some states such as Florida veterinary practice laws require pets to be seen every year to maintain a required doctor patient relationship. The Avma has written that annual physicals are as important to pets as water.

  2. Art Malernee dvm says:

    Sorry, I thought I put my coment above in the over Dx section.

  3. L says:

    I had a dog that was totally healthy till 9 1/2 years. Good diet, exercise, minimal vaccinations. Diagnosed with hemangiosarcoma, 1 month left, no treatment options.
    I will always wonder if it would have made a difference, if her disease could have been picked up if I had taken her in for senior lab work at age 7.
    This dog never had any symptoms, so my other dogs that had issues got all the attention.

  4. skeptvet says:

    Unfortunately, there is no data to answer this question. It is helpful, though, to consider a few things:

    1. Labwork will not detect hemangiosarcoma, The only way to do that would be abdominal and cardiac ultrasound and chest x-rays.

    2. Doing these imaging tests on every senior dog would mean hundreds of dollars in testing (about $750 at our clinic) every year for a disease that is quite rare, so it’s not realistic and is likely to waste a lot of money that isn’t then available for truly necessary testing and treatment.

    3. In humans, imaging like this on people without clinical symptoms is clearly shown to hurt more people than it helps. Lesions are found which aren’t going to cause disease, but people have fear and anxiety, biopsies, sometimes even surgery or chemotherapy anyway because it’s impossible to ignore a lesions once it’s been found.

    4. I have seen many dogs diagnosed with masses on ultrasound who had no symptoms, and often the owners chose not to intervene. Many of those dogs never had disease associated with those masses, so the only effect of finding them was to make the owners worry. And some of those dogs had biopsies and surgery for those masses, which caused pain and expense without benefitting their health.

    So it is important to remember that while individual cases are unpredictable, and anecdotes are very emotionally moving, the reality is we have good reason to think some of our screening tests hurt more patients than they help, and we have to act on that knowledge for the benefit of our patients.

  5. L says:

    Thank you, for your response. I did hear a clicking sound that started a few months prior to diagnosis. It sounded cardiac to me, but when I mentioned it to the vet during a routine heartworm check…. they didn’t hear it and weren’t concerned. It was an odd distinctive sound.
    You never know, I just had my 7 year old poodle mix checked, lab work normal, even though an old rotten back molar tooth popped out (I brush my dogs teeth daily) she does not need a cleaning! Brushing the teeth daily does help, they may still need a cleaning or two within their lifetime though, depends on genetics.

  6. skeptvet says:

    Ann Emerg Med. 2017 May 2. pii: S0196-0644(17)30264-0. doi: 10.1016/j.annemergmed.2017.03.006. [Epub ahead of print]
    Levocetirizine and Prednisone Are Not Superior to Levocetirizine Alone for the Treatment of Acute Urticaria: A Randomized Double-Blind Clinical Trial.
    Barniol C1, Dehours E1, Mallet J1, Houze-Cerfon CH1, Lauque D2, Charpentier S3.
    Author information
    We evaluate the efficacy of a 4-day course of prednisone added to antihistamine for the management of acute urticaria in an emergency department (ED).
    In this double-blind randomized clinical trial, patients were eligible for inclusion if aged 18 years or older and with acute urticaria of no more than 24 hours’ duration. Patients with anaphylaxis or who had received antihistamines or glucocorticoids during the previous 5 days were not included. In addition to levocetirizine (5 mg orally for 5 days), patients were assigned to receive prednisone (40 mg orally for 4 days) or placebo. The primary endpoint of the study was itching relief 2 days after the ED visit, rated on a numeric scale of 0 to 10. Secondary endpoints were rash resolution, relapses, and adverse events.
    A total of 100 patients were included, 50 in each group. Seven patients in the prednisone group and 8 in the placebo group discontinued treatment. At 2-day follow-up, 62% of patients in the prednisone group had an itch score of 0 versus 76% of those in the placebo group (? 14%; 95% confidence interval -31% to 4%). Thirty percent of patients in the prednisone group and 24% in the placebo group reported relapses (? 6%; 95% confidence interval -23% to 11%). Mild adverse events were reported by 12% of patients in the prednisone group and 14% in the placebo group.
    The addition of a prednisone burst did not improve the symptomatic and clinical response of acute urticaria to levocetirizine. This study does not support the addition of corticosteroid to H1 antihistamine as first-line treatment of acute urticaria without angioedema.

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