Progress in Standardization of Immunoassays for Prostate-Specific Antigen

For volunteer, healthy men 50 to 80 years old in the United States, 90% have a serum prostate-specific antigen (PSA) level of 4 ng/mL or less, 8% have a PSA level of 4 to 10 ng/mL, and only 2% have levels higher than 10 ng/mL. Positive biopsy rates for prostate cancer in these three groups are, however, less than 1%, 7 26%, and 53% 3 if systematic, spatially separated biopsies are performed. This extraordinary increase in positive biopsy rates if serum PSA increases to above normal levels explains why PSA is so powerful in screening healthy men for prostate cancer. It also emphasizes why there is an urgent need to standardize immunoassays for PSA. 14