Postprandial Plasma Glucagon Kinetics in Type 2 Diabetes Mellitus: Comparison of Immunoassay and Mass Spectrometry.

Context: Accurate glucagon level measurements are necessary for investigation of mechanisms for postprandial hyperglycemia in type 2 diabetes.
Objective: To evaluate the accuracy of postprandial glucagon level measurements using a sandwich ELISA vs a recently established liquid chromatography-high resolution mass spectrometry (LC-HRMS) method in type 2 diabetes mellitus.
Design and Participants: Twenty patients with type 2 diabetes treated with insulin underwent a meal test before and after administration of the dipeptidyl peptidase-4 inhibitor anagliptin for 4 weeks. Blood samples were taken serially after the meal, and glucagon levels were measured using both ELISA and LC-HRMS. We compared the change from baseline to 4 weeks ( Δ 0-4W) using the area under the curve for plasma glucagon during the meal test [area under the curve (AUC)0-3h] measured using ELISA and LC-HRMS.
Results: ELISA-based glucagon AUC0-3h was higher than LC-HRMS-based AUC0-3h at baseline and 4 weeks. However, differences in Δ 0-4W-AUC0-3h measured using ELISA and LC-HRMS were not statistically significant. Additionally, Δ 0-4W-AUC0-3h measured using ELISA and LC-HRMS were strongly correlated ( r = 0.87, P < 0.001).
Conclusions: Plasma glucagon levels during a meal test in patients with type 2 diabetes measured using ELISA were consistently higher than those measured using LC-HRMS. However, given that the changes in glucagon levels measured using ELISA before and after dipeptidyl peptidase-4 inhibitor therapy were similar to those based on LC-HRMS, this ELISA seems to be useful for evaluating the effect of the drug interventions on postprandial glucagon levels.