Performance Evaluation of a Fully Automated Immunoassay for the Detection of Human Growth Hormone on the Elecsys® Immunoassay System

Background: The aim of the present study was to evaluate the technical performance of a new immunoassay for the detection of human growth hormone. Methods: The Elecsys growth hormone (GH) Immunoassay which is composed of two hGH specific antibodies, one biotinylated monoclonal Ab and one polyclonal Ab coupled with a ruthenium complex, was compared with three currently available automated GH immunoassays. Results: The performance evaluation resulted in an interassay and total imprecision CV between 0.6 - 1.7% and 1.7 - 4.1%, respectively. Using the 20% CV criteria, the functional sensitivity was found at 0.05 mu g/L. Pearson's coefficients of correlation were > 0.98 for method comparison to three established automated GH reagents (A-C). Linear regression according to Passing and Bablok showed larger deviations to reagent A (slopes 1.36 - 1.44), while closer agreement was obtained with reagent B and C. Diagnostic results obtained with the Elecsys (R) hGH assay in various stimulation and suppression tests of patients with growth hormone deficiency and acromegaly compared to healthy controls were in close agreement to established reagents demonstrating high sensitivity and specificity for the diagnosis of growth hormone disorders. Conclusions: The evaluation of the GH immunoassay generated homogeneous performance data but the comparison with three established full automated hGH assays demonstrated a considerable degree of variability suggesting assay specific interpretation in the provocation testing of growth hormone disorders. Obviously, such discrepancies limit the applicability of consensus guidelines. Nevertheless, because of its excellent reproducibility, robustness and the short assay time, the new automated hGH assay represents a major improvement in endocrine diagnosis and treatment in clinical practice.