Improvement of prostate cancer screening by determination of the ratio free/total PSA in addition to PSA levels.

BACKGROUND

The measurement of prostate specific antigen (PSA) is widely used in screening programs for early detection of prostate cancer. However the specificity for cancer detection is limited because serum PSA is also elevated in patients with benign prostatic-hyperplasia (BPH) and/or prostatitis. It has been shown recently, that the ratio of free/total PSA in serum is lower in malignant prostatic disorders than in non-malignant ones and therefore might be a parameter to improve screening specificity. In a retrospective study, we tested whether free/total PSA helps to distinguish between BPH and prostatic carcinoma in men with elevated serum PSA.

METHODS

A total of 266 men have been identified with age-specific elevated serum PSA levels using a conventional PSA determination kit. Subsequently their disease was proven by biopsies. Free and total PSA levels in these serum samples were measured using the DELFIA PSA dual label free/total PSA kit.

RESULTS

The mean free/total PSA of 64 patients with prostate cancer was 0.10 and was significantly (P = 0.001) different from the mean free/total PSA of 202 men who were histologically free of cancer, which was 0.17. Receiver-operating-characteristic curve (ROC) analysis showed that using a free/total PSA ratio of 0.18 as a biopsy criterion in men with an elevated PSA serum level, 37% of the negative biopsies could be eliminated while still detecting 94% of all carcinomas.

CONCLUSIONS

These results show that the ratio of free/total PSA is a useful determination and can improve specificity of prostate cancer screening.