Measurement of prostate specific antigen complexed to α1‐antichymotrypsin to avoid unnecessary biopsy in patients with serum prostate specific antigen levels 4–20 ng/mL

Abstract Aim: To investigate whether measuring prostate specific antigen complexed to α1-Antichymotrypsin (PSA-ACT) can increase sensitivity and specificity in detecting prostate cancer. Methods: In this prospective study, we measured serum total PSA, PSA-ACT, free PSA, prostate volume and transition zone volume on 210 patients with total PSA level of 4–20 ng/mL. From fitted curves between positive predictive values for prostate cancer and age, prostate volume, transition zone volume, total PSA, PSA-ACT or F/T ratio, each function predicting prostate cancer was determined. Relative probabilities for prostate cancer (RPpca) which were defined by combined functions of age, F/T ratio, prostate volume or transition zone volume, and total PSA or PSA-ACT were calculated. Furthermore, using logistic regression, analysis was performed to determine the probability of prostate cancer. Receiver-operating characteristic analysis was performed to clarify the areas under the curve (AUC) for conventional single parameters, RPpca and logistic regression probability. Results: F/T ratio showed the largest AUC among conventional parameters. The AUC of RPpca was larger than those of F/T ratio and logistic regression probability. RPpca using the functions of age, transition zone volume, PSA-ACT and F/T ratio showed the largest AUC and highest specificity at sensitivity 95% level, however, specificities at sensitivity 90% and 85% were identical to those of RPpca using the functions of age, prostate volume, total PSA and F/T ratio. Conclusions: RPpca using the functions of age, transition zone volume, PSA-ACT and F/T ratio was the best way to detect prostate cancer, however, the usefulness of PSA-ACT appears limited, considering the cost.