Prostate specific antigen complexed to α-1-antichymotrypsin in patients with intermediate prostate specific antigen levels

BACKGROUND. The authors attempted to evaluate prospectively the usefulness of serum prostate specific antigen (PSA) complexed to alpha-1-antichymotrypsin (PSA-ACT) in the early detection of prostate carcinoma and its ability to discriminate between prostate carcinoma and benign prostatic hyperplasia (BPH), especially among patients with intermediate PSA levels. METHODS. Between December 1999 and August 2000, systematic sextant biopsies were performed on 281 prospective patients with prostate carcinoma who had serum PSA levels between 4.1 ng/mL and 20.0 ng/mL. The serum samples were assayed by using kits that were designed specifically for measuring serum PSA, PSA-ACT, and free PSA levels. The clinical values of PSA, PSA-ACT, the free PSA to total PSA ratio (F/T ratio), the free PSA to PSA-ACT ratio, PSA density (PSAD), and PSA-ACT density (ACTD) were compared by using receiver operating characteristic (ROC) curve analysis. RESULTS. Biopsy yielded no evidence of malignancy in 198 patients, and prostate carcinoma was confirmed in 83 patients. ROC analysis demonstrated that the area under the curve (AUC) for PSA-ACT was greater than that for total PSA and was equivalent to that for the F/T ratio in both groups of patients (PSA ranges of 4.1-20.0 ng/mL and 4.1-10.0 ng/mL, respectively). The AUC for the ACTD was greater than the AUC for the PSAD and had the highest value of all parameters. CONCLUSIONS. The measurement of PSA-ACT represents an alternative to the use of total and free PSA. The ACTD value is the most useful for discriminating between BPH and prostate carcinoma. (C) 2002 American Cancer Society