Free to total prostate-specific antigen (PSA) ratio is superior to total-PSA in differentiating benign prostate hypertrophy from prostate cancer.

Background: Serum prostate-specific antigen (PSA) exists in different molecular forms, and their respective concentration has been proposed as a useful tool to improve discrimination between benign prostatic hypertrophy (BPH) and prostate cancer (PC).
Methods: The relevance of the free to total PSA ratio was prospectively studied in a selected urology clinic population of 420 patients. Total serum PSA ranged from 2.1 to 30 ng/ml; 154 had PC and 266 had BPH.
Results: Receiver operating characteristic (ROC) curves were constructed for the total population (total-PSA range from 2.1 to 30 ng/ml) and for the diagnostic gray zone of 2.1-10 ng/ml. For the two groups, the free to total PSA ratio had a higher specificity than total-PSA for all sensitivity levels. Cut-off values were found to, vary with prostate weight.
Conclusions: Although free to total PSA ratio demonstrated better performances than total-PSA, its use in screening appears problematic, due to the low prevalence of prostate cancer.