Preliminary results of clinical evaluation of the free/total prostate-specific antigen ratio in a multicentric study

Aims and background: The free/total (F/T) prostate-specific antigen (PSA) ratio is probably the most promising tool proposed to increase the specificity of PSA in the diagnosis of prostate cancer. The aim of the present study was to evaluate the clinical value of the F/T ratio in 138 patients with benign hyperplasia, 101 with untreated prostate cancer, and 175 apparently healthy men. Methods: We used a new immunometric assay of free PSA (FPSA-RIACT, CIS Diagnostici, Italy) which has shown good analytical performance; sample handling and storage under routine conditions did not affect the antigen stability. Results: The diagnostic efficiency of the fifth total PSA ranging from 4 to 10 ng/ml, at a specificity level of 95% total PSA showed a sensitivity of 7%, whereas the sensitivity of F/T increased to 70%. Using the F/T ratio as a decision tool in association with total PSA and considering all cases candidate to biopsy (total PSA greater than 3.79 ng/ml corresponding to the 95% level), we demonstrated a 35% reduction of total biopsies that would have been required on the basis of total PSA alone. Conclusions: The determination of the percentage of F/T serum PSA significantly improves the specificity of the marker, particularly in the 4-10 ng/ml dose range where unnecessary prostate biopsies can be reduced.