Endocrine Abstracts

Introduction: Circulating insulin levels are widely used to provide diagnostic information for diabetes mellitus and hypoglycaemic syndromes. C-peptide concentration provides an accurate assessment of residual B-cell function and reliable information about insulin secretion in patients with diabetes. The aim of this study was to evaluate the performances and reliability of the Liaison^® fully automated system for measurement of insulin and C-peptide concentrations.

Methods: Insulin and C-peptide concentrations were measured with the Liaison^® system (Diasorin) using immunoassays based on chemiluminescence detection. For methods comparison, 81 patients with insulin concentrations previously determined with the Immulite assay and 82 patients with C-peptides levels measured by RIAs were included. The reliability of Liaison^® assays was confirmed with 135 other patient specimens requested for simultaneous determination of insulin and C-peptide.

Results: A positive and significant correlation was observed between the two insulin assays (r=0.95; P<0.0001) and the Passing and Bablock regression analysis provides a slope of 1.03 and an intercept of −1.52. The two C-peptides were also significantly correlated (r=0.95; P<0.0001) and the Passing and Bablock regression analysis provides a slope of 1.29 and an intercept of −0.07. In the 135 patients followed for both parameters, mean C-peptide concentrations were 0.93, 1.35 and 1.73 pmol/ml for insulin concentrations between 3 and 10 μUI/ml (n=44), between 10 and 20 μUI/ml (n=48) and higher than 20 μUI/ml (n=29), respectively. In patients with insulin below 3 μUI/ml (n=13), C-peptide were suppressed (<0.05) in eight patients and detectable in five patients.

Conclusions: The results of this preliminary study demonstrate that the performance characteristics of the Liaison^® insulin and C-peptide assays allow their use for the clinical assessment of diabetes, hypoglycemia and insulin secretion. Nevertheless, larger studies are required to confirm those results and the specificity of these assays.