The value of free and total prostate specific antigen in identifying patients for prostatic biopsy and its relationship to Gleason score and number of positive cores.

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.