EVALUATION OF PROSTASURE INDEX IN THE DETECTION OF PROSTATE-CANCER - A PRELIMINARY-REPORT

Objectives. Although prostate-specific antigen (PSA) has revolutionize d the detection of prostate cancer, it has definite limitations with r espect to its clinical sensitivity and specificity. Because a substant ial number (20% to 40%) of men undergoing radical prostatectomy have a PSA level of 4.0 ng/mL or less, any new test offering diagnostic impr ovement must perform well in patients whose PSA level is less than or equal to 4.0 ng/mL, as well as in patients whose PSA is greater than 4 .0 ng/mL. The performances of two tests, the ProstAsure index and the percent free PSA test, were evaluated in detecting cancer. Methods. We retrospectively analyzed serum samples from 225 men who were grouped into three categories: 94 men who had a normal digital rectal examinat ion and a serum PSA level of 4.0 ng/mL or less, 77 men who were clinic ally suspected of having benign prostatic hyperplasia (BPH) with a ser um PSA level of 4.0 ng/mL or less, and 54 men with localized prostate cancer. The PSA assays were performed using the Hybritech and Tosoh as says and the ProstAsure index was determined by Global Health Net, Sav annah, Ga. Receiver operator characteristic (ROC) corves were construc ted to evaluate the performance of these two tests, and the areas unde r the curve were compared for significance. Results. The sensitivity a nd specificity of detecting prostate cancer using ProstAsure were 93% and 81%, respectively. Using a cutoff Value of 15%, the sensitivity an d specificity of detecting cancer for percent free PSA were 80% and 74 %, respectively (sensitivity increased to 93% and specificity to 59% f or free PSA at 19%). In men with a total serum PSA level of 4.0 ng/mL or less, ProstAsure had a lower false-positive rate compared to free P SA level at 19% for men with or without clinical BPH as well as for me n without clinical BPH using a 15% free PSA threshold. ProstAsure left fewer cancers undetected (7%) compared to free PSA at the 15% cutoff (20%). Conclusions. In this study of selected men, ROC curve analysis shows a statistically significant advantage in performance (P = 0.0023 ) for the ProstAsure index compared to free PSA in detecting prostate cancer. (C) 1998, Elsevier Science Inc. All rights reserved.