Variation of serum prostate-specific antigen levels: an evaluation of year-to-year fluctuations

Blood levels of prostate-specific antigen (PSA) may change from month to month and year to year, according to a study of 972 men. Men who had an abnormal PSA test result during one visit had a normal one during a follow-up visit. This is especially likely to happen in men with only a moderate elevation, between 4 and 10 nanograms per mililiter. PSA is a test for prostate cancer.