ANALYTICAL PERFORMANCE OF THE TANDEM(R)-R FREE PSA IMMUNOASSAY MEASURING FREE PROSTATE-SPECIFIC ANTIGEN

The analytical performance of the Tandem(R)-R free PSA assay available from Hybritech Inc. was evaluated. Comparison of recoveries of purifi ed free (unbound) prostate-specific antigen (PSA) diluted in female se rum in the Tandem-R free PSA assay and the Tandem-R (total) PSA assay demonstrated a link in calibration between the assays and an accurate determination of percent free PSA. The cross-reactivity of the assay t o purified PSA-alpha(1)-antichymotrypsin was determined to be < 1%. Th e minimum-detectable concentration was < 0.05 mu g/L. The within-run a nd between-day CVs were less than or equal to 5% for samples with > 0. 3 mu g/L free PSA. Dilution and recovery showed no significant deviati ons from linearity across the assay range. The assay was insensitive t o interference from blood components. The Tandem-R free PSA kit was sh own to be an accurate, precise, and reliable assay for the measurement of free PSA.