Screening Tests-Scientific Ambiguity or CAM Certainty

One of my favorite encounters with CAM was when a woman brought an old golden retriever to see me because her energy practitioner told her she had detected leukemia, a kind of white blood cell cancer. Though the pet had no signs of illness at all, I ran a number of tests that failed to show any evidence of leukemia. A year later, the pet came back with a slight cough, and again the energy practitioner had told the owner there was cancer, probably in the lung this time. No such cancer appeared on x-rays, and the cough went away when the dog was treated for a bacterial upper respiratory infection. I asked the owner what had happened with the lymphoma that was previously “diagnosed” by her alternative provider. It turns out, not only was the energy practitioner not mistaken, she had apparently diagnosed lymphoma that was undetectable to the scientific methods I used and then cured it with homeopathy and manipulation of the patient’s energy.

Now this is fun all by itself. The quack will predict that an old golden retriever has cancer every year. Whenever the prediction is wrong, the energy healer will get credit for preventing the disease. But, sooner or later, the dog probably will get cancer, since it is a common disease in the aged and in that breed. When that happens, she’ll get credit for predicting it, and probably for palliating its symptoms and delaying the course. How do you get a racket like that?!

But, more seriously, this raises the question of how decide what screening tests to run in a given patient. Running bloodwork to look for leukemia in a symptom-free animal is pointless. The disease isn’t common, and it’s usually rapidly progressive so it makes the patient sick pretty fast. Testing clinically normal animals won’t likely find any leukemia cases, and it also won’t guarantee that the animals we test won’t get leukemia next week. It’s probably a harmless waste of $45 since the risk from drawing a blood sample is negligible, but it’s still unnecessary.

It is generally of questionable value to run screening tests blindly in apparently healthy animals. A study in Germany1 looked at bloodwork taken prior to anesthesia in over 1500 dogs and found that “the changes revealed by pre-operative screening were usually of little clinical relevance and did not prompt major changes to the anesthetic technique…In dogs, pre-anesthetic laboratory examination is unlikely to yield additional important information if no potential problems are identified in the history and on physical examination.” The study did show, however, that there were some “abnormal” results, and if those results led to delay in surgical treatment or to unnecessary diagnostics, then there could potentially be a cost to such screening.

In fact, sometimes the costs of tests that are not indicated by some specific clinical suspicion can be quite high. A recent study in the Annals of Family Medicine, covered in more detail on the Science-Based Medicine blog, found that the cumulative risk of undergoing unnecessary invasive diagnostic tests as a result of false positive results in several common screening tests for cancer was 29% in men and 22% in women over 3 years. These people had to cope with the anxiety of thinking they might have cancer, and with the risks of invasive diagnostic tests, when in fact the screening test was wrong. Harriet Hall has done a fine job of illustrating the same problem with screening asymptomatic patients in her discussion of prostate cancer and the PSA test. As with all things in the real world, benefits come with risks, and an appropriate balance between the two comes only from careful study and constant re-examination and revision of clinical practices.

Certainly screening tests, properly used, can save lives. But such tests are seldom as definitive as the public tends to think, and they are not without their risks. At least, in scientific medicine, an effort is made to determine when such tests are indicated, when their benefits outweigh their costs. In CAM, this is rarely the case. Chiropractic booths offering free spinal screenings are ubiquitous at county fairs, farmer‘s markets and other such venues, and shockingly every single person who gets “tested” turns out to have something that needs fixing. CAM practitioners are remarkable in their ability to find problems in apparently healthy patients. But as the anecdote I started with illustrates, they have some advantages over science-based medicine when it comes to such screening tests.

If you apply a CAM test to a healthy patient and find a subluxation, unbalanced Ch’i,
or some other result that no one else can confirm or deny, you may create some anxiety, and you will very likely expose the patient to the expense, and sometimes risk of treatment. But ultimately you can do whatever magic you do, declare the patient cured and the follow-up test results normal, and your client will likely thank you. You will certainly never have to face the awkward situation of not being able to find a lesion, and having the patient of pet owner decide you must be incompetent because they “know” something is wrong. And you will never have to agonize over whether running the test in the first place will do more harm than good, or whether false positive results might lead you to perform ultimately unnecessary diagnostics or treatments. And, as I’ve suggested before, you will have the advantage of a satisfyingly simply and clear narrative to offer, with no uncertainties. Yet another example of how CAM practitioners avoid the whole unpleasant issue of truth and fiction, and manage to make clients happy and themselves a nice living without all the bother of the constant questioning, self-doubt, and paradigm revision of real medicine.

1. Alef, M.,von Praun, F., Oechtering, G. Is routine pre-anesthetic haematological and biochemical screening justified in dogs? Vet Anesth Anal 2008; 35:132-140.

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4 Responses to Screening Tests-Scientific Ambiguity or CAM Certainty

  1. Skeptico says:

    So we have an imaginary illness. But don’t worry, we can cure it with an imaginary therapy. Perfect.

    Funny thing though, I bet they won’t take imaginary money to pay for it. That has to be the real stuff.

  2. Bartimaeus says:

    My favorite story of quackery is a client who spent an unknown but probably considerable amount to have a “pet psychic” in Australia read her pets aura via a picture emailed to her. She then sold the owner some type of vitamin supplement to correct the aura. This client was the type who usually questioned every charge and fussed about the cost of everything, no matter how small. Of course, the fact that the psychic was halfway around the world made her that much more attractive to the client. Here in Arizona, no one uses “Hopi ear candles”, but I hear they are quite popular in Europe and Australia. Something exotic is always better than the familiar.

  3. skeptvet says:

    Absolutely! The “Ancient Wisdom of the East” sells well in the West despite its waning popularity in “The East.”

  4. Pingback: Short and Sour–Politics & Fear Trump Evidence « The SkeptVet Blog

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