On call: Measuring the PSA Is... Health Article

On call

Q. I have always had my blood tests taken the first thing in the morning, before I’ve had breakfast. We’ve just moved to a new home and I’ll have a long commute to the hospital, so I’d like to eat before I start out. My cholesterol has always been great, so my doctor said a light breakfast won’t interfere with cholesterol tests. But he didn’t know if eating would change my PSA result. What do you think?

A. At last — a PSA question with a simple, un­equivocal answer: Breakfast will not affect your PSA result, nor will lunch or dinner. In June 2005, doctors proved the point by measuring PSA levels three times over the course of a single day in 80 patients with an average age of 62 years. The samples were obtained before breakfast, after breakfast, and after lunch — and there were no changes in the PSA results.

Over the years, researchers have investigated other things that may affect PSA results. A doctor’s digital rectal exam will not alter blood PSA levels, nor will riding a bicycle. On the other hand, ejaculation may temporarily boost the PSA, so if your reading is high, it may be wise to repeat it after 48 hours of abstinence. Urinary tract infections can send the PSA soaring, as can prostate biopsies and other procedures involving the lower urinary tract.

Doctors have figured out when to draw blood for the PSA test, but they are still working on the much harder questions of whether to draw it and how to interpret the results.

— Harvey B. Simon, M.D. Editor, Harvard Men’s Health Watch