Screening – Illiterate Physicians May Do More Harm Than Good

Kenneth Lin

Posted 3/05/12 on Common Sense Family Doctor

On the first day of the clinical preventive medicine course that I teach every spring, I review the concept of lead-time bias and its potential to make a screening test look more effective than it really is (or, effective when it’s not). Frugal Family Doctor recently explained how lead-time bias deceptively improves 5-year survival statistics. If you are unfamiliar with this concept, I recommend reading his post, but the basic idea is that by advancing the time in the disease course that cancer (or some other condition) is detected, screening will always increase the percentage of patients who survive for 5 years or more, even if it doesn’t do anything to reduce mortality. This concept is as basic to the appropriate use of screening tests as vital signs are to the practice of medicine. In my opinion, any physicians who don’t understand lead-time bias ought to have their test-ordering privileges suspended until they do.

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