Tuesday, August 28, 2012

Are Medical Tests Overused?

     There have recently been a slew of articles about the overuse of  medical testing. Special attention has been directed towards radiological studies (including in-office ultrasound) and OTC testing kits sold to consumers. However, none of these articles takes the patients' views and wishes into account.

     One philosophical question arises when the patient asks for a test, blood or radiological, which the physician knows will be negative. Is there anything ethically wrong in ordering this test to give the patient peace of mind, assuming that the physician explains the probability of a false negative test and the problems and possible morbidity that can follow from acting on a false positive test? I think not. In some cases a negative test (e.g. a cardiac stress test in a patient suffering chest pain from a panic attack) will permit the physician to direct the patient's attention to the underlying problem. This is especially true in irritable bowel syndrome, where it has been my experience that it is very difficult for the patient to agree that the symptoms are purely functional.

     The thought of some diseases strikes such terror in patients' minds that they insist on screening tests, even though no study has shown that a positive test leads to a clinical intervention that either saves or prolongs life. Screening for ovarian cancer with the CA-125 blood test plus a vaginal ultrasound immediately comes to mind. OTOH, abdominal aortic aneurysms do enlarge, rupture and kill the patient (as in the case of Albert Einstein who refused surgical treatment). Medicare will pay for one abdominal USG in a patient's lifetime if the first test is normal. "Cost effectiveness" would limit this study to the highest risk group: male smokers over 65, especially if they have hypertension. However, although the group  incidence published in an article in Lancet was 11%, I am certain that if a patient was told that he/she had a 5% chance of having a possibly fatal condition, then they would want the ultrasound.

     We do know how to treat many infectious diseases, so screening for tuberculosis, syphilis, AIDS, hepatitis B and Hepatitis C, all of which can be fatal if untreated, would seem to make sense, although there are no studies as to how often these tests should be offered if negative. One would think that screening for chronic kidney disease, which problem can lead to dialysis, would also make sense, but in the latest issue of the Annals of Internal Medicine the United States Public Service Task Force has come out against this. We can't even show that screening for diabetes saves lives, but we are on firm ground when we state that treating hypertension prevents strokes. Oddly enough, although untreated high blood pressure can cause heart failure, there is no clinical study that demonstrates that treating hypertension prevents heart failure. And although "everyone" agrees that a chest Xray is not needed in a non-smoker with no pulmonary symptoms, many anesthesiologists insist on a chest Xray before surgery if general anesthesia is to be used.

     Every female of child-bearing age who comes to the emergency room is given a urine test for pregnancy. Should the same be done at every visit to a physician's office? Or before any Xray, including dental ones?
The prevalence of arteriosclerotic coronary artery disease at autopsy in 40 year old men is 10%. Should every man of this age have a stress-echo cardiogram as well as a thallium stress test? What about smokers and insulin-dependent diabetics and morbidly obese patients at age 30?

     It makes clinical sense to do a complete blood count, because anemia can be treated and its cause found, and many leukemias can be cured. Similarly, deficiencies of vitamin B12, vitamin D and iron  can be tested for and treated, as can elevated mercury, uric acid, and  calcium levels as well as  low magnesium levels. Whether patients who grew up in a country where parasites are endemic or who visited such countries should be screened for parasites has never been properly addressed, and such patients are usually only tested when they evince symptoms. I assume the physician would obtain the patient's permission before testing for such drugs as cocaine, amphetamines, opiates and benzodiazapenes. Another debated practice is that of obtaining a baseline EKG at the first office visit: no patient ever has a completely "normal" EKG, and it can make clinical sense to know what the EKG looks like before the patient's first visit to the ER with chest pain. And annual EKG's can detect the occurrence of a silent MI, but no studies have, to my knowledge, addressed the utility of this practice, although an unchanged EKG does bring a degree of mental comfort to the patient.

     I have saved the thorniest problem for last. There are more and more OTC tests sold for patients to test themselves not only for a particular disease, but for risk factors for the disease. This is a real problem if the disease in question has no satisfactory treatment. And unless the false positive and false negative percentages are explicitly stated on the package along with the prevalence of the disease in the patient's population, he may well be needlessly worried or reassured. Clearly these tests will continue to be sold, but the patient should be firmly instructed by the pharmacist not to jump to any conclusions before discussing the results with his/her physician.

     Let me close with an anecdote from my practice. When you donate blood, the Red Cross routinely screens for AIDS among other diseases, and confirms a positive screen with a Western Blot test which is the  "gold standard". The WB is not used for screening because it is more expensive and labor intensive, much as syphilis is screened for with the VDRL and confirmed with the FTA. In the past, the flu virus for the vaccine was grown in human cell culture, and because of cross-viral antibodies, patients who received the flu vaccine would test positive for the AIDS virus on the screening test but negative on the Western Blot; this false positive existed for three to six weeks after the flu vaccine. I received a panicked phone call one December from a patient of mine who was a fraternity member at a Florida university where the fraternities were competing with one another in a blood bank drive. He told me that he and 25% of his brothers had tested positive on the screen, and what were they to do? Thankfully I was able to reassure him about the false positive once I had learned that they had all gotten the flu vaccine the previous week, and could tell him to wait for the Western Blot result. Of course, he could never again give blood, because although the Red Cross would officially tell them the Western Blot was negative and that they didn't have AIDS, they still would not risk using the blood.


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