Evaluation of serologic disease markers in a population-based cohort of patients with ulcerative colitis and Crohn's disease

Background: The sensitivity of assays for antineutrophil cytoplasmic antibo dy (ANCA), anti-Saccharomyces cerevisiae antibody (ASCA), and antipancreati c antibody (PAB) in different laboratories is unknown. Likewise, the sensit ivity and diagnostic usefulness of these assays in patients with inflammato ry bowel disease (IBD) in the community is unknown. Methods: An incidence c ohort of 290 patients with IBD were offered participation in the study. Blo od was obtained from 162 patients (56%) (83 with ulcerative colitis, 79 wit h Crohn's disease) who agreed to participate. ANCA was determined in five l aboratories, ASCA in two laboratories, and PAB in one laboratory. Results: In ulcerative colitis, the sensitivity of ANCA determined in five laborator ies varied widely, ranging from 0-63%. In Crohn's disease, the sensitivity of ASCA determined in two laboratories did not vary significantly, ranging from 39-44%; and the sensitivity of PAB determined in one laboratory was 15 %. The optimal diagnostic usefulness was obtained from one laboratory where the positive predictive values of a positive ANCA assay combined with a ne gative ASCA assay for ulcerative colitis, and a negative ANCA combined with a positive ASCA for Crohn's disease, were 75% and 86%, respectively, Concl usions: In patients with IBD, the sensitivity of ANCA varied widely in diff erent laboratories, whereas the prevalence of ASCA was similar. The positiv e predictive values of the ANCA assay combined with the ASCA assay for ulce rative colitis and Crohn's disease are high enough to be clinically useful.