Supplementary Material for: Autoantibodies are useful in monitoring disease activity and predicting relapses in autoimmune pancreatitis

INTRODUCTION
Autoimmune pancreatitis (AiP) is an inflammatory disease typically treated with corticosteroids. But repeated corticosteroid treatment (CST) can cause significant side effects, raising the need for better management strategies. This study investigated the role of ‘conventional’ autoantibodies in monitoring disease activity and progression in AiP to establish individualized treatment strategies.
METHODS
The study examined 55 AiP patients from the University Medical Centre Mannheim (Germany) and aimed to correlate ‘conventional’ autoantibodies with disease severity, relapse risk, and other clinical parameters by analyzing 769 treatment appointments.
RESULTS
56% of AiP patients have elevated levels of ‘conventional’ autoantibodies, particularly smooth muscle antibody, anti-neutrophil cytoplasmic antibodies (ANCA), and rheumatoid factor. Rheumatoid factor was especially elevated in AiP type 1, whereas ANCA was elevated in AiP type 2. An increased disease activity is assumed in case of high AiP Activity-Score, before (vs. after) CST, in the case of emergency (vs. elective) treatment and in presence of other organ involvement. Autoantibodies were found to correlate with these clinical markers of disease activity. Furthermore, symptomatic inflammatory bowel disease in AiP type 2 was associated with increased ANCA titers. The presence of a focal mass was especially associated with an increase in rheumatoid factor. Notably, patients with elevated autoantibodies at baseline and particularly those with insufficient reduction of autoantibody titers after CST had a higher likelihood of relapse.
CONCLUSION
While conventional autoantibodies are not diagnostic for AiP, they are useful in monitoring disease activity and predicting relapse. Testing for autoantibodies could help guide individual treatment decisions.