Letters; May 2012; Scientific American Magazine; by The Editors; 2 Page(s)

SCREENING STATS
During my 30-year practice of diagnostic radiology, I spent many hours educating physicians and surgeons on the importance of false positives and false negatives in the diagnostic process. No diagnostic test is 100 percent accurate. My mantra was always: don’t treat initial test results. Always confirm the diagnosis with other independent data before performing surgery or prescribing pharmaceuticals with serious side effects.

I applaud the general theme of mathematician John Allen Paulos in “Weighing the Positives” [Advances]. First he makes the valid argument that medical tests will be positive for some patients without disease. He then illustrates this with a statistical analysis of mammography on one million patients, resulting in 9,960 false positives. He makes a monumental error, however, in stating, “If the 9,960 healthy people are subjected to harmful treatments ranging from surgery to chemotherapy to radiation, the net benefit of the tests might very well be negative.”