There is evidence that the association of anti-PR3 with IBD/PSC may be related to the specific immunoassay used (e.g., ELISA versus chemiluminescence) and the possibility that novel epitopes of the target PR3 in PSC/IBD may not be available for autoantibody binding in ELISA (Stinton et al., 2014). This evidence concerns the gene PRTN3 and inflammatory bowel disease.