Significance of free to total PSA ratio in men with slightly elevated serum PSA levels: A cooperative study

Background: The ratio of free PSA in total PSA (fit) has been reported to improve the diagnostic accuracy of prostate cancer in the group with slightly elevated serum PSA values. In Japanese cases, the clinical significance of f/t is still controversial. Methods: The diagnostic significance of fit in serum for prostate cancer was evaluated in a cooperative study. A total of 77 cases with prostate cancer and 224 with non-prostate cancer showing less than 20 ng/ml of total PSA were evaluated. Results: Serum total and free PSA values were not affected by storage at 25 degrees C for 2 days, The determination of fit was useful in the cases with a serum total PSA of 5.1-10 ng/ml; the specificity was 60% with a sensitivity of 90% at an f/t of 0.148, The positive predictive value for diagnosis of prostate cancer also increased to 54% from 34% of that in total PSA alone. In the range of 4.1-10 ng/ml, the cut-off value of f/t was 0.155 for obtaining relatively high specificity; sensitivity was 85% and specificity was 56.5%. Conclusions: Thus, the determination of f/t was considered to be an effective tool for discriminating the non-prostate cancer cases from those of prostate cancer.