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 i mprove the diagnostic accuracy of prostate cancer in the group with slightl y elevated serum PSA values. In Japanese cases, the clinical significance o f f/t is still controversial. Methods: The diagnostic significance of fit in serum for prostate cancer wa s evaluated in a cooperative study. A total of 77 cases with prostate cance r 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 wit h a serum total PSA of 5.1-10 ng/ml; the specificity was 60% with a sensiti vity 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 alo ne. In the range of 4.1-10 ng/ml, the cut-off value of f/t was 0.155 for ob taining relatively high specificity; sensitivity was 85% and specificity wa s 56.5%. Conclusions: Thus, the determination of f/t was considered to be an effecti ve tool for discriminating the non-prostate cancer cases from those of pros tate cancer.