Diagnostic efficacy of free SPA/total PSA ratio in the diagnosis of prostatic carcinoma.

Prostate specific antigen, specific organ and tissue marker, is a glycoprotein present in serum in different molecular forms, i.e. not protein bound and bound to proteins (PSA-ACT and PSA-AMG). The total PSA is expressed by the sum of the non protein bound value (free-PSA) and PSA-ACT. The aim of our study was to evaluate the hypothesis that measurement of free/total PSA ratio may be helpful in the differential diagnosis of prostatic pathology. Our study was conducted on 350 patients, to whom the total-PSA, free-PSA and f/t PSA had been performed; 250 patients showed a total PSA between 2.5 and 10 ng/ml and 185 of them had symptoms of bladder out-flow obstruction. In all of the 250 patients digital rectal examination, transrectal ultrasound and prostatic biopsy were performed. 100 patients were controls. The cut-off to differentiate between benign and malignant prostatic disease was 16%. The pathologic diagnosis was related to the f/t PSA ratio, and in particular those patients with a f/t PSA lower than 16% were expected to be prostatic carcinoma, while those with a f/t PSA higher than 16% were expected to be benign prostatic hypertrophy. The diagnostic accuracy of the ratio was calculated, and it was observed that it was 88.65% in the diagnosis of benign prostatic hypertrophy, while in the diagnosis of prostatic carcinoma it was 84.5%. We can therefore assume that f/t PSA can add useful information on prostatic pathology, eventually sparing unnecessary prostatic biopsies.