Using predictive value, sensitivity and specificity to interpret laboratory tests: PSA for the diagnosis of prostate cancer.

The Prostate Cancer Prevention Trial yields a means to evaluate PSA screening for prostate cancer detection. The receiver operating characteristic curve shows that PSA above 2.5 provides optimum sensitivity and specificity for prostate cancer diagnosis by needle biopsy. However, the maximum positive predictive value of 48% occurs at PSA above 4.0 and does not increase at higher PSA cutpoints. Consideration of test sensitivity and specificity alone is not sufficient for optimal interpretation of test results.