Comparative study of ASCA (Anti-Saccharomyces cerevisiae antibody) assays in inflammatory bowel disease

Background &Aims: Anti-Saccharomyces cerevisiae antibody (ASCA) is a serolo gic marker associated with Crohn's disease (CD), Although there is still di scussion on its clinical value, several companies each promote their own AS CA assay to be used in the gastroenterologist's practice at considerable ex pense. The aim of this study was to determine whether different ASCA assays agree sufficiently well for the results to be used interchangeably, Method s: Blood obtained from a large cohort of IBD patients with inflammatory bow el disease (IBD; 100 with CD, 100 with ulcerative colitis [UCI]) and 178 co ntrols (100 healthy blood donors and 78 patients with non-IBD diarrheal ill nesses) was studied with 4 different ASCA assays, Sensitivity, specificity, and positive predictive value were compared. Agreement between assays was evaluated. Results: Sensitivity of ASCA for CD ranged between 41% and 76%. Sensitivity was inversely related to specificity and positive predictive va lue. Results correlated well overall (range 0.54-0.90) and the different RO C curves showed good agreement, When recalculated cutoff points were used, interchangeability increased. However, large differences were seen when abs olute values were compared. Conclusions: A large range in sensitivities and specificities of ASCA for CD is seen with different ASCA assays, mainly as a consequence of the cutoff value chosen for each individual assay. Althou gh agreement between and within assays is good, caution is important when a bsolute values are used. Standardization of ASCA measurements is greatly ne eded.