An Interobserver Study on IgG4 Related Disease
Travis L Rice-Stitt, Yoh Zen, Vikram Deshpande. Massachusetts General Hospital, Boston; King's College Hospital, London, United Kingdom
Background: IgG4 related disease (IgG4-RD) is a multisystem multiorgan inflammatory disease that responds to immunosuppressive therapy. The common organs involved include the pancreas, biliary tract, lung, lymph nodes, and kidney. In part, the diagnosis is dependent on histopathological features: dense lymphoplasmacytic infiltrate, obliterative phlebitis and storiform type of fibrosis. However, there are organ based variations in the histopathological appearance. A quantitative analysis of a tissue IgG4 stain is widely accepted and indispensable test for the diagnosis of IgG4-RD; however, there are no widely accepted cut points. The purpose of this study was to prospectively evaluate interobserver agreement on the histopathological diagnosis of IgG4-RD.
Design: Sixteen pathologists participated in this study. A virtual library of 31 biopsies and resection specimens was constructed. Readers reviewed the slides online and filled out a questionnaire for histopathologic findings and diagnosis. The study group included 20 cases of IgG4-RD and 11 mimics of this process. The specimens in this data set included: liver (6), kidney (4), salivary gland (4), lymph node (4), aorta (3), lung (3), orbit (4), and retroperitoneal fibrosis (3). The readers were provided an H&E slide, an immunohistochemical stain for IgG4 and an IgG4 to IgG ratio.
Results: The overall kappa coefficient was 0.775 (substantial/good agreement). The kappa value for pathologists that sign out a single subspecialty was lower than those who evaluate ≥ 2 specialties (p=NS). However, there was a wide variation in the cut points for IgG4 used by the pathologists for the diagnosis of IgG4-RD. The two commonest histological features used by the pathologist included a dense lymphoplasmacytic infiltrate and a storiform type fibrosis.
Conclusions: We demonstrate substantial κ agreement in the diagnosis of IgG4-RD among pathologists with an interest in IgG4-RD.
Monday, March 19, 2012 1:00 PM
Poster Session II # 105, Monday Afternoon