New study suggests reconsidering IgG4 cutoff values for better pancreatic disease diagnosis

Higher IgG4 cutoff levels reduce diagnostic accuracy for autoimmune pancreatitis (AIP), according to a poster presented at the American College of Gastroenterology 2024 Annual Meeting.

Researchers reviewed electronic health records (EHRs) to identify patients who underwent IgG4 testing. They used macros to extract relevant diagnoses, such as AIP, pancreatic insufficiency, cysts, and pancreatic lesions. Patients were further evaluated based on the Mayo Clinic HISORt criteria for AIP to classify them as likely or unlikely cases.

Out of 1,333 patients tested, the number of IgG4 tests increased more than 13-fold from 2011 to 2019. However, only 1.5% and 0.6% of patients had IgG4 levels exceeding 2 and 3 times the upper limit of normal (ULN), respectively. The study found that higher IgG4 thresholds had lower diagnostic accuracy, with a decrease in sensitivity at elevated cutoff values. The optimal diagnostic cutoff identified was 100 mg/dL, yielding a robust area under the curve of 0.8. In addition, no cases of pancreatic malignancy were detected with IgG4 levels above 2x ULN, and only 5% of malignancy cases had modest IgG4 elevations between 1-2x ULN.

Reference
Chaudhry R, et al. Accuracy and Diagnostic Yield of Serum IgG4 Testing in the Evaluation of Pancreatic Disease Poster presented at: American College of Gastroenterology 2024 Annual Meeting; October 25-30, 2024; Philadelphia, PA.