Evaluation of the serum testosterone to prostate-specific antigen ratio as a predictor of prostate cancer risk

Study Type - Diagnostic (exploratory cohort) Level of Evidence 2b Objective To analyse the ratio of serum testosterone (sT) to prostate-specific antigen (PSA) as a predictor of prostate cancer risk, as low levels of sT have been related to a greater risk of prostate cancer, and its ratio with serum PSA level was recently proposed as a new tool to increase the specificity of PSA. Patients and Methods In all, 439 consecutive men with a normal digital rectal examination and a serum PSA level of 4.1-20 ng/mL had a transrectal ultrasonography-guided biopsy using a 10-core scheme, with an additional 1-8 cores according to prostate volume and patient age. The sT level was determined before the procedure using a chemiluminescent assay, and the ratio of sT to PSA (sT/PSA) was calculated after transforming sT measurements from ng/dL to ng/mL. The percentage free PSA (%fPSA) and PSA density were also included in this analysis. Results The overall cancer detection rate was 42.1%. The median sT level was 469 ng/dL in men with cancer and 499 ng/dL in those without (P = 0.521). The median sT/PSA was 0.68 and 0.74, respectively (P = 0.215). However, the median %fPSA was 14 in men with cancer and 17 in men without (P < 0.001) and the median PSA density was 0.22 and 0.16, respectively (P < 0.001). The multivariate analysis confirmed the independent predictive value only for %fPSA (odds ratio 0.94, 95% confidence interval 0.91-0.98) and PSA density (5.8, 3.42-19.8). Conclusion These results do not support the use of sT/PSA for predicting the risk of prostate cancer and to increase the specificity of PSA. © 2009 BJU INTERNATIONAL.