NEW AUTOMATED DIRECT CHEMILUMINESCENT IMMUNOASSAY FOR THE DETERMINATION OF SERUM TESTOSTERONE

ACS(TM) Testosterone, a new chemiluminescent immunoassay (CLIA) for th e determination of serum testosterone was evaluated and compared with a standard radioimmunoassay (RIA) routinely used in our laboratory. Th e ACS Testosterone assay was developed for use with the ACS:180(R) ben chtop immunoassay analyzer (Ciba Coming). The system uses chemilumines cent labels as tracers and paramagnetic particles as solid-phase reage nts. The precision of ACS Testosterone within the series was below 5% (coefficient of variation [CV]) at all dose levels, and inter-assay CV s were between 6 and 12%, with lower concentrations exhibiting higher variation. Serial dilutions of multidiluent spiked with known amounts of testosterone showed excellent parallelism with the master curve and good agreement between expected and observed testosterone concentrati ons, thus demonstrating high accuracy. Sensitivity, as assessed by det ermination of serum containing no testosterone, was 0.55 nmol testoste rone/L (16 ng/dL). Functional sensitivity was estimated to be between 0.75 to 1.0 nmol/L (22-29 ng/dL). Parallel determination of 101 patien t samples with the ACS Testosterone and an established RIA method reve aled excellent agreement (r = 0.987, slope 0.899, intercept 0.097). Cr ossreactivity for 5 alpha-dihydrotestosterone was below 5%. ACS Testos terone is not affected by sample hemolysis. Using sera from 50 apparen tly healthy men and women, reference ranges were established. The uppe r limit of normal for premenopausal women was 2.5 nmol/L and for postm enopausal women 1.8 nmol/L. For healthy men, age-dependent reference r anges were established. The clinical utility of ACS Testosterone was d emonstrated by finding serum testosterone concentrations of hypogonada l men and hyperandrogenic women in the expected range. In summary, bec ause of its excellent precision, accuracy, and sensitivity, the ACS Te stosterone assay is highly suitable for routine use in the determinati on of serum testosterone. The combination ,vith the automated ACS:180 immunoanalyzer makes this system very attractive for laboratories with large volumes of testosterone determinations and a need for rapid res ults.