(ASCA) and against neutrophils (pANCA) has been used as diagnostic serological markers for inflammatory bowel disease (IBD) for many years. The combination of a positive ASCA test with a negative pANCA test has a positive predictive value of 96% and a specificity of 97% for Crohn’s disease (CD). 1 However, both antibodies have been found in other diseases, such as autoimmune liver disease, primary sclerosing cholangitis (pANCA), and in gluten sensitive enteropathy (ASCA). Therefore, their role as diagnostic serological markers for IBD seems to be limited.

Antibody determination is of interest in patients with indeterminate colitis. However, almost 50% of these patients do not develop ASCA or pANCA antibodies whereas in antibody positive patients, ASCA+/pANCAJ predicts CD in 80% of patients with indeterminate colitis and ASCAJ/pANCA+ predicts ulcerative colitis (UC) in 64%. 2 Generation of both antibodies is poorly understood. Several studies have shown that titres of both antibodies do not correlate with disease activity, as known from classical autoimmune disease. Antibody titres seem to be stable over long periods of time. Surprisingly, pANCA in UC persist after colectomy, 3 and we have observed patients who have had their last flare up of CD more than 20 years ago and currently display normal findings in gastroscopy, colonoscopy, and histology, but still have high titres of ASCA. Thus these antibodies seem to represent stable serological markers. The only clinical parameter confirmed by several groups is the correlation between ASCA positivity and ileal involvement of disease and penetration as well as structuring disease behaviour. 4