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.
Prague, Czech Republic
24 - 28 Apr 2010
European Society of Endocrinology