Includes measurement of Total PSA and Free PSA by the Hybritech methods, and calculation of Percent Free PSA as follows: %Free PSA = 100 x (Free/Total). Percent Free PSA is indicated primarily with Total PSA results in the 3-10 ng/mL range. Generally %Free PSA levels of 20% or more suggest a higher probability of BPH whereas levels of 10% or less reflect a higher probability of prostatic carcinoma (see table below). This test requires ICD9 codes and waivers. Please refer to the Marshfield Clinic Lab Order Sheet for further information. The following table indicates the Probability of Prostate Cancer for Total PSA's in the 4-10 range and various %Free PSA Levels for men with a non-suspect digital rectal exam: Probability of Prostate Cancer based on Age and %Free PSA
% FREE PSA 50-64 YEARS 65-75 YEARS
0.0 - 10.0% 56% 55%
10.1 - 15.0% 24% 35%
15.1 - 20.0% 17% 23%
20.1 - 25.0% 10% 20%
>25.0% 5% 9%