Evaluation of an enhanced chemiluminescence immunoassay for total serum testosterone using the Vitros ECi analyzer

We report on the evaluation of the new labeled-hapten competitive chemilumi nescence immunoassay for total testosterone in serum applied to the Vitros ECi analyzer (Ortho-Clinical Diagnostics, Inc.). The detection mode uses th e well-established chemiluminescence technology of the Amerlite system. Sig nal generation is performed using a horseradish peroxidase-labeled testoste rone conjugate, the enzyme activity being quantified by an enhanced chemilu minometric method. The ECi analyzer is a continuous, random, and STAT acces s immunoanalyzer. Both single step and two step assays with varying incubat ion times are accommodated. The calibrators for the new testosterone assay are adjusted against the isotope dilution-gas chromatography/mass spectrome try reference method. This ensures accuracy and linearity across the measur ing range of this androgenic steroid. Measuring range is from zero to 75 nmol/L, an excellent linearity of serial dilutions can be demonstrated. The functional sensitivity was found to be 0.30 nmol/L and the interassay imprecision was 5-13%. Accuracy determinatio ns in reference specimens gave a mean recovery of 98%. An influence of rais ed sex hormone binding globulin concentrations on the testosterone measurem ents could be observed. The clinical sample study confirmed that the ECi as say is a sensitive test for the detection of moderately elevated testostero ne levels in hirsute women as well as suppressed testosterone levels in orc hiectomized prostatic cancer patients. Thus, this enhanced chemiluminescenc e immunoassay is suitable for measuring total testosterone in serum under r outine conditions.