Abstract:

Objective To investigate the comparability of serum insulin level detected by five widely used chemiluminescence immunoassay systems, and to further investigate the feasibility of a common parameter not influenced by detection systems. Methods One hundred patients were included who had done insulin release test (no exogenous insulin therapy), and insulin concentrations of the same individual at different time points in oral glucose tolerance test(OGTT) were measured simultaneously by 5 different chemiluminescence immunoassay systems(CLIA, ECLIA, CMIA, CLEIA1 and CLEIA2, respectively), and the ratio of serum insulin levels after meal at each time point to corresponding fasting levels(Ratio) was calculated. Results Temporally compared, there is overall significant difference for serum insulin level among all systems at any time point(all P=0.000); further comparison between any two systems revealed that there was no significant difference for fasting level between the following systems: ECLIA and CLIA, CMIA and CLIA(P>0.05). Similarity was also found between ECLIA and CLIA at 3 h after meal(P>0.05). For Ratio, apart from the more scattered diagram between CLEIA1 and anyone of the other systems, more gathered scatter diagrams were found between any two of the other systems. There was no significant difference between the Ratio by systems of CLEIA2 and ECLIA at 0.5 h after meal(P>0.05), and similar phenomena were found between CLEIA2 and CMIA at 1.0 h, 2.0 h,and 3.0 h after meal(P>0.05). There were significant differences between any other two systems at any time point(all P<0.05. Conclusion Serum insulin levels measured by different chemiluminescence immunoassay systems differ a lot from one another, and could hardly be interoperable though either two systems highly correlated with each other. Nevertheless, between certain two systems, and at certain temporal point, the absolute value of serum insulin or Ratios were able to substitute one for another. The conversion to Ratio from insulin level might help to increase the comparability among different systems.

Key words: insulin, common parameter, chemiluminescence immunoassay