Numerous studies evaluating different populations have shown similar findings with respect to repeated PSA measurements and PSAV. First, there is substantial within-individual variability between repeated PSA measures. Second, this variability between PSA measurements precludes the use of a simple change in PSA as a marker for prostate cancer. Third, when one adjusts the changes that occur in PSA over an elapsed time of 1.5 to 2 years (PSAV), less than 5% of men without prostate cancer will have a PSAV of 0.75 ng/mL/ y or greater, and approximately 70% of men with prostate cancer will have a PSAV of 0.75 ng/mL/ y or greater. These data strongly suggest that PSAV is a specific marker for the presence of prostate cancer.