Blog | Tuesday, November 15, 2011

A brief clarification on PSA testing


The recent recommendation released by the U.S. Preventative Services Task Force against using the PSA blood test to screen for prostate cancer has left many patients confused, and many doctors unsurprised. We've known for a while that in the aggregate, the data do not show that screening for prostate cancer using the PSA test saves lives. We've also known that it may lead to complications of treatment.

Learning how to screen for and successfully treat this cancer is an ongoing project. For example, some of the negatives of screening (that it leads to invasive procedures with significant side effects) can be mitigated as our procedures continue to improve.

But that's a discussion for another time.

What I'm finding my patients asking is "Should I get a PSA test and why?"

The most important clarification before answering this question is explaining the difference between a screening test and a diagnostic test. Screening, by definition, looks at people without symptoms for any signs of disease. If a man is having urinary symptoms--difficulty emptying his bladder, frequent urination, decreased stream, and other--checking a PSA is no longer a screening test. It is a diagnostic test, and the entire current debate is largely irrelevant.

If you have urinary symptoms you are not using a PSA to screen for cancer, but to look for it in someone who has symptoms pointing toward a prostate disorder. That's a very different situation requiring a different set of questions.

Peter A. Lipson, ACP Member, is a practicing internist and teaching physician in Southeast Michigan. After graduating from Rush Medical College in Chicago, he completed his internal medicine residency at Northwestern Memorial Hospital. This post first appeared at his blog, White Coat Underground. The blog, which has been around in various forms since 2007, offers "musings on the intersection of science, medicine, and culture." His writing focuses on the difference between science-based medicine and "everything else," but also speaks to the day-to-day practice of medicine, fatherhood, and whatever else migrates from his head to his keyboard.