[Significance of re-measurement of prostate specific antigen before prostate biopsy]

To examine the natural change of prostate-specific antigen (PSA), we compared two PSA values, the first value with which we decided to perform prostate biopsy and the value obtained by remeasurement just before biopsy. To exclude cases with extremely high PSA, we examined 288 cases in which PSA was less than 50 ng/ml for comparison. Of the 288 cases, 93 were diagnosed with prostate cancer (CaP). The interval between the two PSA measurements was 1-90 days (average of 31.4 days). The first and second values were an average of 13.0 and 11.7 ng/ml, respectively, and the second value was significantly lower than the first value. When we divided them into CaP cases and non-CaPthe two cases, a significant difference between PSA values was found only in the non-CaP cases. Moreover, in the non-CaP cases with some clinical symptoms, the difference in PSA was marked between the first and second values, which averaged 11.2 and 9.2 ng/ml, respectively. When we decide to perform a biopsy, we should recognize that PSA sometimes is lower on re-measurement. Particularly in symptomatic cases, it is worth re-measuring PSA, which may save unnecessary biopsies.