Prostate-specific Antigen (PSA), Free:Total Ratio
In their study, Dr. Catalona and coworkers found that one in four patients with normal DRE and PSA levels between 4.0 and 10.0 ng/mL have prostate cancer ( JAMA. 1998 May 20; 279(19):1542-1547.) They recommend using a cutoff of 25% free PSA for this group of men to identify individuals with an increased risk of prostate cancer. They found that 95% of men with cancer (as determined by biopsy) with normal DRE and total PSA between 4.0 and 10.0 ng/mL had percent free PSA of ≤25%. Their study further indicated that 20% of men with benign disease (as determined by biopsy) with normal DRE and a total PSA between 4.0 and 10.0 ng/mL had percent free PSA greater than the 25% cutoff. The 25% free PSA cutoff detected 95% of cancers while avoiding 20% of unnecessary biopsies.