The Cost of a Pap Smear

"A year is the time it takes for the earth to make a complete revolution around the sun. It has very little to do with the cervix."

I heard an excellent talk today about Dr. Sawaya for the Clinical Sciences elective. He researches the societal cost-benefit relationships of screening tests like the Pap smear. For a long time, women over 18 were encouraged to get annual Pap smears, a test that looks for cervical cell dysplasia, a precursor to cancer. This translates to a lot of Pap smears, far more than is done in any other country.

In analyzing data from a CDC study, Dr. Sawaya found that women who have three consecutive normal Pap smears may not need further annual tests; in this case, tests every three years may be nearly as effective. If Pap smears are done annually, the rate of false positives exceeds that of true positives, and the "cost" (financial, risk during further tests like colposcopy, stress and anxiety) may not justify such a regimen in a non-high-risk woman. If we do Pap smears every three years rather than annually, we may miss 12 cases of cervical cell dysplasia per 100,000 people and 1 cancer per 100,000 people. However, we gain on the order of a million dollars annually per 100,000 people. Cervical cancer takes something like ten years to develop from cervical cell dysplasia so annual vigilance may not seem completely rational.

In the end, no matter how many tests we do, we will miss some people. The question is how low our threshold should be. There are many policy decision-analysis models to look at this. Should we invest over a million dollars to catch 12 people per 100,000 with worrying cervical dysplasia, one of whom will progress to cervical cancer? I'm not convinced. We are a society that does too many tests without regard to the general health of the health care system.