ANALYTICAL PERFORMANCE AND CLINICAL VALIDITY OF 2 FREE PROSTATE-SPECIFIC ANTIGEN ASSAYS COMPARED

We compared two recently introduced commercial assays (CanAg and Immul ite) for measuring free prostate-specific antigen (f-PSA), total PSA ( t-PSA), and the ratio of t-PSA/f-PSA (f-PSA%) in control materials and sera of 54 healthy men, 50 patients with benign prostatic hyperplasia (BPH), and 45 patients with prostate cancer (PCa). The lower detectio n limits for f-PSA were 0.038 mu g/L and 0.004 mu g/L for the CanAg an d Immulite assays, respectively, The within-run and between-day precis ions of the Immulite assay were <5%; the CanAg assay showed a poorer p recision, Whereas f-PSA values differed between controls and patients but not between BPH and PCa patients, the f-PSA% values were lower in PCa patients than in BPH patients and controls, The receiver-operating characteristic (ROC) curve showed an improved diagnostic power of f-P SA% compared with t-PSA to discriminate between BPH and PCa. Discrimin ation limits of 16% (CanAg assay) and 15% (Immulite assay) are recomme nded for f-PSA%.