Assessment of a chemiluminescence immunoassay for antimitochondrial antibody subtype M2 in the diagnosis of primary biliary cholangitis.

INTRODUCTION: We sought to evaluate the diagnostic performance of and interassay agreement between a chemiluminescence immunoassay for antimitochondrial antibody subtype M2 (AMA-M2) in patients with primary biliary cholangitis and clinically relevant disease controls with other liver diseases. METHODS: In this retrospective study, 164 patients with primary biliary cholangitis and 403 patients with other liver diseases were enrolled between December 2020 and January 2023. The AMAs were detected using indirect immunofluorescence, line immunoassay (LIA), and chemiluminescence immunoassay. Diagnostic performance was evaluated by sensitivity, specificity, accuracy, and receiver operating characteristic curve analysis. Agreement between methods was assessed using the Cohen κ coefficient and correlation analysis. RESULTS: AMA-M2 detected by chemiluminescence immunoassay had a sensitivity of 84.1%, a specificity of 90.1%, and an accuracy of 88.4%. Our receiver operating characteristic curve analysis showed an area under the curve of 0.927 (95% CI, 0.903-0.951) for AMA-M2 by chemiluminescence immunoassay, which was higher than the area under the curves for AMA-M2 by LIA (0.772) and M2-3E by LIA (0.862) (both P < .001). High concordance was observed between AMA-M2 by chemiluminescence immunoassay and M2-3E by LIA (96.1%, κ = 0.908), with a strong correlation between the 2 assays. DISCUSSION: Chemiluminescence immunoassay-based detection of AMA-M2 showed high diagnostic performance and strong agreement with conventional assays in this cohort, supporting its utility as a reliable quantitative method for clinical diagnosis.