Background: Serum immunoglobulin G (IgG) level is elevated in autoimmune liver diseases (AILDs), especially autoimmune hepatitis (AIH). However, its utility is limited in current practice as different criteria propose different cut-off values leading to considerable ambiguity.
Materials and methods: A cross-sectional study was conducted among patients with AILD who underwent a liver biopsy over a ten-year period. From 17644 liver biopsies, 630 patients were included and divided into three groups-AIH (455 patients), primary biliary cholangitis (PBC) (97 patients), and overlap (78 patients). Clinical and laboratory details were collected and histological findings were reviewed. Non-cirrhotic non-alcoholic steatohepatitis (NASH) cases were taken as the control group for IgG level comparison.
Results: Among AIH patients, IgG values of >2 times the upper limit of normal (ULN) were associated with significant elevation of aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), bilirubin, and necroinflammatory activity. IgG level of >1.1 times ULN lacks specificity in differentiating AIH from the control group. The receiver operating characteristic (ROC) curve demonstrates maximum sensitivity and specificity at a cut-off value of >1.3 times ULN.
Conclusion: Serum IgG cut-off value for diagnosing AIH, either in isolation or as a component of overlap syndrome, needs revision and uniformity. IgG value of >2 times ULN in AIH is associated with severe AIH. A new cut-off value of >1.3 times ULN is proposed.
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