Automated Immunoassay for Testosterone Evaluated

A new electrochemiluminescence testosterone immunoassay has been evaluated and compared with existing methods.

The competitive immunoassay uses high affinity sheep monoclonal testosterone-specific antibody, which is complexed with the serum samples, and after processing the chemiluminescent emissions are measured by a photomultiplier.

Scientists at the University Medical Center Göttingen, (German), collaborated with others medical centers to evaluate the second-generation electrochemiluminescence assay and compare it to a validated assay. The scientists investigated the within-run precision, total precision, and method comparisons to the former immunoassay and the liquid chromatography tandem mass spectrometry (LC-MS/MS) assay. They were also interested in establishing reference intervals for adults and children. Special attention was paid to females with acute renal failure.

The within-run precision and total precision were determined using five different and site-specific human serum pools and two quality control samples. The within-run imprecision ranged from 12.8 μg/L, (0.9%) to 0.23 μg/L (5.2%), and total imprecision ranged from 12.7 μg/L (2.2%) to 0.22 μg/L (8.5%). The recovery according to quality control sample target values was 2.51 μg/L (95.4%) at one center, and 6.30 μg/L (103.6%) at another.

The new Elecsys Testo II assay (Roche Diagnostics GmbH, Mannheim, Germany) was compared against the former Roche Elecsys Testo assay and to a validated LC-MS/MS assay. Precision was improved especially at concentrations below 2.0 μg/L when compared to the former Elecsys Testo assay. The measuring range of 0.12 μg/L to 15.0 μg/L fulfils clinical needs. The new Elecsys Testo II assay demonstrated superior agreement in comparison to the validated LC-MS/MS method indicating an improved specificity.

Surprisingly, some high testosterone concentrations were found in samples from female patients, as confirmed by LC-MS/MS, as these individuals were suffering from polycystic ovary (PCO) syndrome or even androgen-producing tumors. The authors noted that overestimated values, especially with the former Elecsys immunoassay as compared to LC-MS/MS, were found to be from patients suffering from end-stage renal disease undergoing hemodialysis. The study was published in February 2011, in Clinical Biochemistry.

Related Links:
University Medical Center Göttingen
Roche Diagnostics