[Examination of prostate biopsy among Japanese with less than 4.0 ng/ml prostate specific antigen--usefulness of free/total PSA ratio].

: The low specificity of the prostate specific antigen (PSA) test is considered to be a problem when PSA measurement alone is performed to detect cancer. Therefore, we examined a method to decrease the number of unnecessary biopsies while maintaining the power of the test by using PSA, PSA free/total ratio (PSAf/t), and digital rectal examination (DRE). The subjects were 232 patients with PSA levels of 4.0 ng/ml or less who underwent biopsy for prostate cancer. An endorectal ultrasound perineal biopsy was conducted, and the average biopsy core number was 21. Cancer was detected in 37 of the 232 subjects. Receiver operating characteristic curves of PSA and PSAf/t were subsequently determined. Although the area under the curve (AUC) was 0.56 for PSA alone, the AUC increased to 0.75 when the factor of positive data in DRE was taken into account. Although the AUC was 0.62 for PSAf/t alone, when the factor of positive data in DRE was added as for PSA, the AUC increased to 0.79. In addition, as a result of examining the combination of PSA, PSAf/t and DRE, the condition of the biopsy for prostate cancer in the cases with PSA of 4.0 ng/ml was determined as follows: PSA should be 3.1 ng/ml or more and PSAf/t 27% or less, or the result of DRE should be positive. Based on these criteria, the sensitivity, specificity and detection rate of cancer increased to 0.919, 0.436 and 23.2%, respectively. We consider that this approach will be useful.