The Dark Side of Screening: A new book called Should I Be Tested for Cancer?: Maybe Not and Here's Why takes a look at cancer screening and the fallacy that all testing is good testing:

Dr. Welch also has much to say about those who perform the testing. In a discussion of false-positive results, which plague all common screening tests, he writes, 'No one knows for sure, but I suspect that most American radiologists err on the side of calling things abnormal, in part for fear of being sued, which in turns leads to higher false-positive rates.'

On the P.S.A. blood test for prostate cancer, he notes that the most common cause of false positives is an enlarged prostate. But, he adds, 'Because the prostate tends to enlarge with age, P.S.A.'s tend to rise with age. Therefore, false-positives are less common in younger men and more common in older men.'

Pathologists' role in diagnosing cancer is also problem. They may disagree on a diagnosis because they look at different things, Dr. Welch surmises, 'or they look at the same thing and see something different.'

There's a cardiologist at my hospital who is incapable of interpreting a test as normal. If she reads an echocardiogram or a stress test, there's always some equivocation - the images are of poor quality, or the patient's stress test was "suboptimal," or she mentions some non-specific finding that needs "clinical corelation." It's maddening.