Introduction and objectives: The percentage of free over total prostate specific antigen (%F/T PSA) seems to enhance the predictive value of PSA in diagnosing prostate cancer. We evaluated the value of F/T PSA in 50 consecutive patients who underwent prostate needle biopsy, its relationship to the Gleason score and number of positive cores.
Material and methods: 50 patients underwent prostate needle biopsy for abnormal PSA and/or abnormal digital rectal examination (DRE). There were 8 patients with PSA equal or less than 4 ng/ml, 6 with F/T PSA < 20%, group I (GI). 27 patients with PSA between 4.1 ng/ml and 10.0 ng/ml, 20 with F/T PSA < 20%, group II (GII) and 15 patients with PSA > 10.1 ng/ml (13 with F/T PSA < 20%), group III (GIII). At least six needle biopsies were obtained guided by transrectal ultrasound selectively or randomly. Pathological evaluation included Gleason grade and number of cores involved.
Results: 21/50 patients (42%) had positive biopsies, 3/8 in GI, 8/27 in GII (6 had negative DRE) and 10/15 in GIII (9 had positive DRE). 19/21 patients with positive biopsies had F/T PSA < 20%. The sensitivity, specificity and positive predictive value of PSA between 4-10 ng/ml and F/T PSA < 20% was 87.5%, 31% and 35% respectively. Stratifying patients with positive biopsies to F/T PSA < 10%, F/T PSA > 10% and the three PSA groups, there was no relationship to either Gleason score or number of positive cores.
Conclusion: With a cutoff of 20%, F/T PSA seems to be an important parameter in selecting patients with abnormal PSA for biopsy. It will be helpful mostly with PSA 4-10 ng/ml. No relationship was observed between the level of F/T PSA, grade or number of positive cores.