B-125 Beta-2 IgG4 score: a novel index for screening elevated IgG4 levels using capillary zone electrophoresis-immunosubtraction

Abstract Background The diagnosis of IgG4-related disease (IgG4-RD) is challenging due to its diverse clinical manifestations. In practice, IgG4-RD is often overlooked as a differential diagnosis, and IgG4 tests are infrequently ordered. Previous studies have demonstrated that serum protein electrophoresis, a more commonly ordered test, can reveal distinct patterns in individuals with elevated IgG4 and help prompt the consideration of IgG4-RD. However, the promotion of this approach has been hindered by the absence of standardized interpretation criteria. Method This study introduced a novel index, the “Beta-2 IgG4 Score,” for screening individuals with high IgG4 levels using capillary zone electrophoresis-immunosubtraction (CZE-IS) results. The Beta-2 IgG4 Score was defined as the proportion of the beta-2 peak amplitude attributable to IgG. To assess diagnostic performance, this study retrospectively reviewed specimens with concurrent CZE-IS and IgG4 (as the reference method) measurements collected from 2023 to 2024. Results A total of 427 specimens were analyzed, with 46.9% originating from male patients. The median age was 58 years (interquartile range: 44–69). Among these specimens, 111 exhibited elevated IgG4 levels, while 28 had very high IgG4 levels (defined as >5 times the upper limit of normal). The Beta-2 IgG4 Score demonstrated an area under the receiver operating characteristic curve of 81.6% for detecting elevated IgG4 levels and 84.2% for detecting very high IgG4 levels. Conclusion The Beta-2 IgG4 Score provides a simple and effective method for screening IgG4 elevation using CZE-IS, facilitating the early diagnosis of IgG4-RD.