• Folks across the country are paying hard cash for total body scans, abdominal aortic aneurysm testing, CAT coronary artery scans and carotid artery evaluations to prevent disease or find important lesions early. Ordinary patients don’t understand about pre-test probability and positive and negative predictive values. A critical principle of proper diagnostic testing can be summarized in a single sentence.
• If an individual is unlikely to have the medical condition under consideration, then a diagnostic test that yields a positive result is likely to be a false reading.
• Here is an illustration demonstrating why patients need to understand this issue.
• A 30-year-old non-smoker sees me in the office with chest pain that is readily relieved with antacids. It is very unlikely to be angina, and probably represents simple heartburn. If I arrange for this person to undergo a cardiac stress test, and the result is positive, then it is much more likely that the test result is wrong than that the individual has true heart disease. This is not simply my opinion, but a conclusion based upon mathematical and statistical principles. Such a patient can easily slide, or be pushed, down a medical cascade that may include cardiac catheterization, or even stenting of a coronary artery that was not responsible for the patient’s symptoms, and should have been left alone.
• The key is that diagnostic tests need to be ordered when the patient has a reasonable chance of having the condition under consideration. This determination is made on the basis of a careful history and physician examination. When stress tests and various scans are ordered casually by physicians, or requested by patients, then this opens a pathway into a medical labyrinth with no easy way out. Would you prefer to agonize over a false positive test result that pushes you toward medical quicksand, or avoid an unnecessary test in the first place?
• Of course, there are rare individuals who have benefited from a scan that was ordered for the wrong reasons. These folks understandably are convinced that the scan saved their lives. Should every person undergo a CAT scan of the head every year because it is theoretically possible that a few might benefit by accident?
• Total body scans, and all of their cousins, are examples of medicine at its worst. It is a commercial enterprise that bypasses sound medical principles and judgment. These entrepreneurs proffer a promise that they know they cannot fulfill. It’s a scam clad in a white coat. Many patients who have endured on the medical cascade may feel that they were rescued from certain disaster.  I’d rather rescue folks from the cascade.

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