Serologiske markører ved inflammatorisk tarmsykdom

Abstract

SEROLOGICAL MARKERS IN INFLAMMATORY BOWEL DISEASES

Background Correct diagnosis of inflammatory bowel disease (IBD), especially the differentiation between Crohn`s disease (CD) and ulcerative colitis (UC), is highly important toward treatment and prognosis. Serological markers are noninvasive diagnostic tools that could be of value in differentiating CD from UC, and in the identification of IBD cases. Perinuclear antineutrophil cytoplasmic autoantibodies (pANCA) have been suggested as a serological marker for UC, and anti-Saccharomyces cerevisiae antibodies (ASCA) have been suggested as a serological marker for CD. Variable prevalences have been reported from different countries. The prevalence of these markers has not yet been studied in a Norwegian cohort of patiens with established IBD.

Aims To examine the prevalence and diagnostic value of serologic markers in a Norwegian cohort of patients with established IBD, using a group of patients with non-IBD illnesses as controls. In addition, we wanted to examine whether these antibodies could be related to a specific clinical phenotype or course of disease in IBD.

Methods Sera from 173 patients with established IBD and 170 patients with non-IBD illnesses were evaluated for the presence of ASCA and pANCA. Immune marker status was determined by investigators blinded to clinical characteristics, and all clinical variables were extracted retrospectively from hospital records by one investigator.

Results ASCA was positive in 48% of CD vs. 17% in UC, p<0.001. On the other hand pANCA was positive in 43% of UC as compared to 16% of CD, p<0.001. These figures are lower compared to most previous studies. The highest specificity for differentiating CD from UC was achieved using the combination of both markers. The combination of ASCA+/pANCA-, had a specificity for CD of 89%, whereas pANCA+/ASCA- had a specificity for UC of 88%. Using multiple regression analyses, ASCA in CD patients were shown to be independently associated with early age of disease onset and small bowel disease as well as fibrostenosing and penetrating disease behaviours.

Conclusions pANCA and ASCA testing are spesific but not sensitive for UC and CD. We found prevalences of the serological markers that were lower than in most studies from other countries. ASCA seems to be a prognostic risk factor for complications in CD. Thus ASCA may prove useful in determining subgroups that would benefit from a more aggressive medical treatment early in the course of CD.