Harvard Men's Health Watch

PSA variability: A new factor

What's your PSA?

It's a simple question, but for many men who choose to have the prostate-specific antigen blood test to screen for prostate cancer, there is no simple answer. That's because PSA levels, like other biological functions, often vary. Since all prostate cells, both benign and malignant, produce the controversial protein, in most cases the swings have nothing to do with prostate cancer. And a new study sheds surprising light on a previously unsuspected reason for PSA variability.

Rapid changes

Short-term variations in the PSA are well-known. Inflammation of the prostate (prostatitis) and urinary tract infections boost the PSA rapidly, often to very high levels. The same is true for medical manipulations that affect the gland, including prostate biopsies and the placement of a Foley catheter in the bladder. A doctor's digital rectal exam (DRE) is a low-tech medical manipulation; some studies suggest that DREs can temporarily elevate blood PSA levels, while others do not.

A man's behavior can also produce short-term changes in his PSA. For example, putting the prostate to work can nudge up PSA readings; when ejaculation elevates PSA results, the effect lasts less than 48 hours, which is why many doctors recommend a few days of abstinence before a blood sample is obtained for testing. Similarly, a vigorous workout on an exercise bike may produce a temporary PSA bump.

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