Diagnostic Criteria for Autoimmune Pancreatitis

Serum IgG4 Levels

• Serum IgG4 >4× upper limit of normal appears highly specific for IgG4-related sclerosing cholangitis (IgG4-SC), a biliary manifestation of the same disease spectrum 1
• An IgG4/IgG1 ratio >0.24 improves specificity for distinguishing IgG4-SC from PSC 1, 2

Histopathological Criteria

• IgG4+/IgG+ plasma cell ratio >40% is a key diagnostic criterion per international consensus 2

Diagnostic Approach

• The American Gastroenterological Association recommends integrating clinical presentation, imaging findings, serum IgG4 level, histopathology when available, and response to corticosteroids for diagnosis, as stated in guidelines similar to those from the National Comprehensive Cancer Network 2, 4