CLINICAL-SIGNIFICANCE OF THE DETERMINATION OF NONCOMPLEXED PROSTATE-SPECIFIC ANTIGEN AS A MARKER FOR PROSTATE CARCINOMA

Objectives. The aim of this study was to investigate whether a signifi cant difference consists between patients with and without prostate ca rcinoma (CaP) regarding the ratio of prostate-specific antigen (PSA) i n complex with major proteinase inhibitors to noncomplexed (free) PSA (FPSA). Methods. We analyzed the sera of 29 patients with untreated Ca P, 34 patients with benign prostatic hyperplasia (BPH), and 33 men wit h no symptoms of prostate disease for the amount of FPSA and total PSA (TPSA) with the Immulite chemiluminescent enzyme immunometric assay. Results. FPSA was found only as a minor fraction in all sera tested. C alculation of the percentage of FPSA from TPSA revealed a significant difference between patients with CaP (median, 9.55%) versus patients w ith BPH (median, 17.07%; P = 0.00001) or versus healthy men (median, 1 6.11%; P = 0.0006). Considering only patients with PSA values less tha n 10 ng/mL, the difference between patients with Cap versus patients w ith BPH remained significant (P = 0.026). The specificity for differen tiation between CaP and BPH at a sensitivity level of 89% for the comb ined evaluation of the proportion of FPSA and TPSA increased from 30% (TPSA considered alone) to 61%. The cutoff level for TPSA was determin ed at 4 ng/ml and for the proportion of FPSA at 21.1%. Conclusions. Th ese data indicate that the differentiation between CaP and BPH can be considerably improved by measuring both FPSA and TPSA and calculating the ratio of the one to the other.