Studies don't all agree, but U.S. researchers say several show a man should avoid sex 48 hours before a prostate-specific antigen test.
The Wellness Letter of The University of California, Berkeley, reported several studies showed ejaculation could falsely increase PSA levels somewhat, at least in men 50 and older -- the age group most screened -- thus misleadingly indicating increased cancer risk.
"Avoiding ejaculation for 48 hours before a PSA test is thus prudent," the newsletter said. "Otherwise you might need to have the test repeated after abstaining if the result comes out elevated, causing unnecessary worry."
Prostate specific antigen is a protein produced in the prostate gland and found at high concentration in semen. The PSA test detects how much is spilling into the blood -- there should be very little -- elevated blood levels may be a sign of cancer, but also of an enlarged prostate or a prostate infection.
However, some drugs used to treat an enlarged prostate could also lower a PSA reading.
"If you are taking finasteride -- Proscar or Propecia, the latter used to treat hair loss -- or dutasteride, or Avodart, remind your doctor before having a PSA test so this can be taken into consideration in the interpretation of the results," the newsletter said.