Current usefulness of free/total PSA ratio in the diagnosis of prostate cancer at an early stage.

The aim of our study was to evaluate five different free/total PSA (f/t PSA) kits for the diagnosis of early stage prostate cancer. We compared the PSA density and the f/t PSA ratio to differentiate between benign prostatic hyperplasia (BPH) and prostate cancer. This prospective study included a total of 120 patients with suspected prostate cancer (PSA between 4 and 15 ng/ml) observed over a period of 30 months. All patients had a blood test as well as a prostate biopsy prior to inclusion. Serum immunoassay total-PSA (t PSA) and free-PSA (f PSA) were carried out using five different assay kits: IMX Abbott (A), Kryptor Brahms (B), Immulite DPC (D), IRMA Immunotech (I) and IRMA DiaSorin (S). The results were compared to determine sensitivity, specificity, threshold values, and to differentiate between BPH and cancer. No difference was found between assay reproducibility and variation in the assays, however, only a slight variation was observed in the mean t PSA values, whereas a significant difference was found with f/t PSA. Receiver operating curves were generated for t-PSA and f/t PSA. The area under the curves did not show any significant differences for either t PSA or f/t PSA. A low comparative variability between the five kits tested for tPSA was observed, which suggest that the f/t PSA ratio has no current usefulness in the initial diagnosis of prostate cancer, particularly in patients with larger prostates. Furthermore, no prognostic value was found for surgically positive margins in radical prostatectomy.