Interassay and Interobserver Variability in the Detection of Anti-Neutrophil Cytoplasmic Antibodies in Patients with Ulcerative Colitis (Technical Briefs‪)‬

Inflammatory bowel disease (IBD) represents a spectrum of disorders that affect the gastrointestinal tract (1). IBD includes two major entities, Crohn disease and ulcerative colitis (UC). Although the etiology of IBD is unknown at present, it is believed to be an immunologically mediated disease (2). Over the last 40 years, various (auto)antibodies have been described in IBD (3). Anti-Saccharomyces cerevisiae antibodies (4) and perinuclear anti-neutrophil cytoplasmic antibodies (pANCAs) (5) have relatively high prevalence in patients with Crohn disease and UC, respectively. Unlike ANCAs present in vasculitis (6) and in Wegener granulomatosis (7), the exact target antigen of UC-associated pANCAs has not been identified (5,8). As a consequence, immunofluorescence microscopy is the only widely available technique for screening for these antibodies. Commercially available substrates, however, are not standardized, and part of the discrepancy in results could be attributable to differences among the substrates/ assays used, as reported recently (9). Moreover, because specific microscopic criteria to distinguish UC-associated pANCAs from pANCAs seen in vasculitis vary among laboratories, discrepant results could also be attributable to an investigator's interpretation of the fluorescence pattern.