A strange “health care” drama plays out daily in our clinics and hospitals. A healthy person has a medical test done (even though he or she is healthy): a blood test, a chest x-ray or mammogram, maybe an ultrasound of some body part. The test comes back abnormal. The patient (for she has now gone from being a healthy person to being a patient) is struck with worry, and undergoes a further round of testing to determine whether the initial, “screening” test was accurate. This more invasive, risky definitive testing causes the patient pain, complications, infections, further procedures to fix the complications. But the testing shows that the original screening test was wrong, and the patient is relieved of their worry and overcome with a sense of gratitude: “Yes, the follow-up surgery was painful, but at least it’s not cancer.” However, notice what caused the worry in the first place: not some symptom that they were experiencing, but a test that was performed on a healthy person. What a marvelous bit of sorcery: we take a happy patient, create unnecessary worry, then win their undying gratitude by performing risk-laden procedures on them to remove their worry!
There is something very intuitive about the concept that detecting a disease (especially cancer) early leads to better outcomes, that screening tests are inherently good. Yet when one studies the actual outcomes of implementing mass screening programs in a population of people who have no signs or symptoms of a particular disease, one finds to one’s surprise that, not infrequently, more people are harmed by our screening test than are helped (See: PSA testing, carotid ultrasounds, annual stress tests, etc).