Analytical and Clinical Performance of a Liquid Chromatography–Tandem Mass Spectrometry Method for Measuring Gastrin Subtypes G34 and G17 in Serum

Background Two major forms of gastrin, gastrin-17 (G17) and gastrin-34 (G34), exist in blood. However, conventional immunoassay methods can only quantify total gastrin or G17 alone. Here, we aimed to establish a liquid chromatography–tandem mass spectrometry (LC–MS/MS) method to quantify G17 and G34 simultaneously. Methods Serum samples were prepared by anion-exchange solid-phase extraction. The analytical performance of the LC–MS/MS method was validated and the method was compared to chemiluminescence immunoassay (CLIA) and radioimmunoassay (RIA). The G17 and G34 concentrations in 245 serum samples from healthy controls, individuals with gastrinoma, and individuals with other diseases were analyzed. Results The total runtime of the LC–MS/MS method was 6 min. No substantial matrix effect was observed with internal standard correction. The intraassay coefficients of variation (CVs) for G17 and G34 were 4.0%–14.2% and 4.4%–10.4%, respectively, and total CVs were 5.2%–14.1% and 4.6%–12.4%, respectively. The correlation coefficient between LC–MS/MS and CLIA was 0.87, and between LC–MS/MS and RIA was 0.84. The G17+G34 concentrations for 87.5% of individuals with gastrinoma were higher than the 95th percentile of healthy controls (18.1 pg/mL), whereas the concentrations for individuals with other diseases and gastrinoma overlapped. Based on the Youden indices calculated for G17+G34, G34, and G17, the most specific biomarker was G17 (96.9% clinical specificity at 209.8 pg/mL) for gastrinoma. Conclusions This method should aid in the diagnosis of diseases associated with increased gastrin concentrations.