Development and validation of a fast and reliable method for the quantification of glucagon by liquid chromatography and tandem mass spectrometry

Introduction: The quantitation of glucagon remains a challenging immunoassay, mainly due to cross-reactivity. A sensitive, rapid and specific intact glucagon method is therefore necessary for quality routine analysis. A tandem mass spectrometry method to fulfill this objective is described in this work. Methods: Glucagon was extracted from plasma employing a mixed-mode anion exchange solid-phase extraction. Sample stability was assessed in K2-EDTA and P800 tubes at different temperatures. We compared our method to two different immunoassays. FDA and EMA guidelines were followed for validation. An external quality control program served for comparison with other laboratories. Results: Assay imprecision was below 4%. Recoveries were within 95-103%. LoQ was 8.75 pg/mL. Total analytical CV was 2.91%. Samples were found stable at 4 degrees C for less than 4 h. Diasource (R) RIA disagreed with our method. Mercodia (R) ELISA provided a closer agreement, also proven by external quality control samples. Conclusions: A rapid and specific LC-MS/MS method for glucagon quantitation has been developed, validated and is suitable to routine care. The simplicity and the good performances in terms of time and specificity, could open the possibility to establish a standardized method for glucagon.