Prostate specific antigen (PSA) elevations predict the presence of prostate
cancer, but test specificity is poor when the PSA is 4 to10 ng/mL. The proportion
of PSA that is free in the serum is lower in prostate cancer than in benign
disease, leading some to suggest that measuring free PSA would enhance diagnostic
utility. In this study of men with PSA 4 to 10 ng/mL, Dr Catalona and colleagues
use a 25% cutoff value for free PSA, which still detected 92% of the cancers
(98% in younger men), and improved the test's overall specificity to 20%.