King's College London

Background: We determined if PR3-ANCA is a biomarker that differentiates ulcerative colitis (UC) from Crohn's disease (CrD). Methods: A total of 946 sera were tested, including 86 granulomatosis with polyangiitis (GPA) and 491 inflammatory bowel disease (IBD) patients (283 UC and 208 CrD), 264 pathological controls (various diseases) and 105 healthy individuals. All samples were tested for PR3-ANCA by ELISA (QUANTA Flash Lite®, INOVA Diagnostics) and chemiluminescent immunoassays (CIA QUANTA Flash PR3). Conventional anti-neutrophil cytoplasmic antibody (ANCA) indirect immunofluorescence assays (IIF) was performed with NOVA Lite™ (INOVA Diagnostics). Results: PR3-ANCA by CIA were detected in 31.1% UC vs. 1.9% CrD sera (p=. 2.2E. -. 16), and by ELISA in 6% UC and 0% CrD (p=. 0.0003). In GPA patients, PR3-ANCA were detected in 75.6% by CIA and 61.6% by ELISA (p