Selected performance characteristics of the Roche Elecsys testosterone II assay on the Modular analytics E 170 analyzer.

Background: Serum testosterone measurements have utility in diagnosis of clinical conditions characterized by both increased and decreased testosterone concentrations. Studies have indicated that testosterone immunoassays may give inaccurate results for women and children. We evaluated the performance of a second generation testosterone immunoassay from Roche Diagnostics.

Methods: Testo II performed on a Modular Analytics E 170 analyzer is an automated random access electrochemiluminometric assay. We evaluated limit of blank (LoB), imprecision, linearity, interference, and method comparison with liquid chromatography-tandem mass spectrometry assay (LC-MS/MS). Method comparison included the current generation Roche testosterone assay (Testo I) and the Access 2 testosterone chemiluminometric assay (Beckman Coulter). Results for men and women were analyzed for analytic concordance. The relative % differences of immunoassay compared to LC-MS/MS results were evaluated.

Results: The LoB was 0.07nmol/l. Total imprecision was <6%. The assay was linear from 0.2 to 46.6nmol/l. Negative interference was observed for lipemia at concentrations >22.5g/l. Analytic concordance showed improved specificity for women. Comparison of results to LC-MS/MS indicated comparable performance with other immunoassays for men and improved performance for women, boys, and girls with mean differences of 0.5%, -0.7%, and 24.4%, respectively.

Conclusions: The Roche Testo II assay demonstrated excellent precision. Comparison to 2 other automated immunoassays showed comparable performance for men and improved performance for women and children. However, challenges still exist for quantifying testosterone concentrations <10.4nmol/l for men and <1.7nmol/l for women and children by immunoassay.