MEASUREMENT OF SERUM PROSTATE-SPECIFIC ANTIGEN USING IMX PROSTATE-SPECIFIC ANTIGEN-ASSAY

The analytical characteristics of singlet determinations of the IMx prostate specific antigen (PSA) assay are similar to the mean of duplicates using the Tandem-Rdouble dagger PSA assay. The 2 assays are standardized equally and provide test results that correlate well (r = 0.9997). The IMx PSA assay is more automated, requires less technologist time and provides faster test results. This assay has a minimal detection limit of 0.02 to 0.04 ng./ml. and functional sensitivity at a 20% coefficient of variation of 0.06 to 0.13 ng./ml. With a sensitive lot of IMx PSA reagents, only 38% of post-radical prostatectomy patients had nondetectable values compared to 60% with the Tandem-R PSA assay. The within-person, biological standard deviation of PSA concentrations in post-radical prostatectomy patients was 0.01 ng./ml. Therefore, with a sensitive assay these low concentration measurements should be reliable for monitoring. However, the clinical use of these low concentrations for early detection of tumor recurrence must await further studies.