Alan J. Wein, MD
Last Modified: September 15, 2002
Dear OncoLink "Ask The Experts,"
The oncologist said that you should not have sex within 72 hours before a PSA test, as this would spike the results. Can you please explain how this occurs? And also how sex affects PSA in general. How could it be that sex spikes the PSA reading for the test, but in general it is not harmful for a prostate cancer patient.
Alan J. Wein, MD, Professor and Chair of the Division of Urology at the University of Pennsylvania School of Medicine, responds:
Studies examining the effect of ejaculation on serum PSA have shown varying effects. For instance, in men aged 30-40 years or younger, both no change and a significant decrease have been reported. However, in the age group in which PSA testing is primarily used for early detection of prostate cancer (50 years and older), ejaculation can lead to an increase in PSA level but could result in a false positive elevation. After 48 hours, the PSA would be expected to return to baseline in most men. A history of sexual activity and a repeat PSA after 48 hours of sexual abstinence may be helpful in the interpretation of serum PSA levels that are minimally elevated. Thus, even though I believe that in most men, ejaculation will not significantly affect the PSA level, I instruct patients to abstain from ejaculation for 2 days prior to PSA testing. However, you must understand that even if sex increases the PSA reading, sex does not have an adverse effect on prostate cancer.