Be sure to read the other side of this debate, Doctor Debate: Wellness testing--More important than ever! by Dr. Fred Metzger.
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The growing trend of "wellness testing" in veterinary medicine concerns me. Tests such as early detection panels, best care panels, junior and senior panels, and preanesthetic panels are becoming a standard of care in our profession. Veterinarians, many major veterinary organizations, pharmaceutical companies, national diagnostic laboratories, and even the media promote wellness testing.
Although the ability to do wellness testing has been around for years, it has only been recently that practitioners have emphasized its role in veterinary medicine. I think there are four reasons for this.
First, wellness testing has financial rewards. Over the years, veterinarians have wrestled with innovative ways of increasing their practice revenue. Wellness testing accomplishes this. Not only can wellness testing increase the utilization of other testing modalities in a practice, it also helps reduce the burden of vaccines for practice profit. It is important for veterinary practices to be financially healthy, but the way we achieve this should not supplant good medicine and should be in the best interest of our patients.
Second, veterinarians often do wellness testing out of a need to protect themselves against lawsuits—so-called defensive medicine. Some veterinarians think it's always a good thing to look for things to be wrong. While many clients also demand routine tests, they are often bolstered by advertisements, veterinary information online, and veterinarians. To some extent, veterinarians have taught their clients to demand these things. And as a profession we've systematically exaggerated the benefits of early diagnosis, which doesn't always improve survival, and, at the same time, we don't always tell our clients there might be downsides to testing.
Third, and most important, is that wellness testing "screens" for disease and, therefore, is good medicine. If we are using the term wellness testing interchangeably with screening, then we need to examine the statistical merits of doing so. The optimal screening tests should be cost-effective, easy to perform, and have high sensitivity (correctly detect most patients with a disease) and specificity (correctly identify most patients that do not have a disease). It is also important to realize that normal test values are usually arbitrarily defined as those occurring within two standard deviations from the mean, thereby ensuring that 5% of healthy pets that have a single screening test will have an abnormal result. As more tests are ordered, the likelihood of a false positive result increases. Therefore, a screening panel containing 20 independent tests in a patient with no disease will yield at least one abnormal result 64% of the time.
Then there is the lead-time bias phenomenon.1 This bias refers to a spurious increase in longevity associated with screening. In other words, the screening test could discover a disease before the patient feels ill, but it does not extend the patient's life. This early detection can artificially inflate survival time by moving up the diagnosis date, making the test appear to be useful even though mortality doesn't change.
And what about the scientific evidence in support of wellness testing being a good disease screening tool? In human medicine, the literature is replete with research showing the flaws with wellness testing.2-5 But in veterinary medicine there is a lack of evidence-based research showing that patients benefit from wellness testing. Recently, two studies in veterinary medicine addressed the issues of wellness testing. Both studies looked at preanesthetic testing and whether the test results affected the way we anesthetize patients. The first study, out of Germany, concluded, "The changes revealed by preoperative screening were usually of little clinical relevance and did not prompt major changes to the anesthetic technique."6 The second study, out of South Africa, concluded that 1) screening of geriatric patients is important and that subclinical disease could be present in nearly 30% of these patients, and 2) the value of preanesthetic screening in veterinary anesthesia still needs to be evaluated in terms of appropriate outcome variables.7 So based on two studies, at least one type of wellness testing (preanesthetic) may not be justified.
THE "WOW FACTOR"
Anecdotal reports are another reason for the sudden emphasis on wellness testing in veterinary medicine. Every veterinarian can tell a story of a patient with subclinical disease identified on routine wellness testing. It is what I call the wow factor: "Wow, I would never have found this if I had not run all of these tests." And for many veterinarians, these positive anecdotes are reason enough to do wellness testing. But what about dogs and cats having invasive procedures (e.g. liver biopsy, bone marrow aspirate) or expensive follow-up tests (e.g. further blood tests, imaging studies) that were found to be normal? How did these patients benefit from wellness testing?
I think veterinary medicine is where human medicine was 20 years ago with respect to wellness testing. Now, doctors are realizing that wellness testing on every patient is not good medicine. As our profession continues to evolve, we must also take a critical look at wellness testing. Without better studies on which to base wellness testing recommendations, efforts to prevent disease may do more harm than good. It's hard to hold off on strategies as seductive as wellness testing to detect early disease in our patients. But if we don't, then we must be prepared to accept the consequences of going to war with the data we have, instead of the data we really need.
David Robbins, DVM
VCA West Bernardo Animal Hospital
11605 Duenda Road, Suite D
San Diego, CA 92127
1. Grimes DA, Schulz KF. Uses and abuses of screening tests. Lancet 2002;359:881-884.
2. Munro J, Booth A, Nicholl J. Routine preoperative testing: a systematic review of the evidence. Health Technol Assess 1997;1(12):i-iv;1-62.
3. Schein OD, Katz J, Bass EB, et al. The value of routine preoperative medical testing before cataract surgery. N Engl J Med 2000;342(3):168-175.
4. Sommerville TE, Murray WB. Information yield from routine pre-operative chest radiography and electrocardiography. S Afr Med J 1992;81(4):190-196.
5. Bouillot JL, Fingerhut A, Paquet JC, et al. Are routine preoperative chest radiographs useful in general surgery? A prospective, multicentre study in 3959 patients. Eur J Surg 1996 Aug;162(8):597-604.
6. Alef M, von Praun F, Oechtering G. Is routine pre-anesthetic haematological and biochemical screening justified in dogs? Vet Anaesth Analg 2008;35(2):132-140.
7. Joubert, KE. Pre-anaesthetic screening of geriatric dogs. J S Afr Vet Assoc 2007;78(1):31-35.