Clinical evaluation of percent free prostate-specific antigen using the AxSYM system in the best analytical scenario

Objective: Percent free prostate-specific antigen (PSA) is a promising tool for prostate cancer (CaP) diagnosis. However, its diagnostic performances have not yet been established. The present study was carried out with the a im of evaluating percent free PSA in the most favourable analytical conditi ons. Materials and Methods: Eighty-eight patients affected by newly diagnosed, u ntreated, primary CaP, and 169 cases with biopsy-confirmed, untreated, beni gn prostatic hypertrophy (BPH) were prospectively enrolled. Abbott AxSYM to tal and free PSA were measured by the same technician using the same instru ment and the same reagent batch. Results: Percent free PSA was more effective than total PSA in differential diagnosis between CaP and BPH in every evaluated dose range of total PSA. In cases with total PSA >4 mu g/l, percent free PSA could have reduced by a bout 50% the rate of unnecessary biopsies with a probably still acceptable 93% cancer detection rate. The likelihood of CaP after the determination of percent free PSA was in fact higher than 50% using cut-off points which pr ovide low sensitivity values (i.e. 58% in men aged 50-59 years). Conclusions: Percent free PSA is superior to total PSA in distinguishing pr imary CaP from BPH in patients with total PSA between 2 and 30 mu g/l and i n reducing the rate of unnecessary biopsies in men with total PSA higher th an 4 mu g/l. However, percent free PSA should be cautiously interpreted in decision making in individual patients since post-test probability is relat ively low in men aged 50-70 years. Copyright (C) 2000 S. Karger AG, Basel.