To Örebro University

Background: Celiac disease (CD) is a chronic immune-mediated enteropathy affecting about 1% of the population worldwide. CD is triggered by ingestion of gluten in genetically predisposed individuals but additional factors (e.g. infections) are required for the disease to develop. CD also seems to be associated with infectious complications.

Aim: The main objective of this thesis was to increase the knowledge about the associations between CD and infections.

Methods: Epidemiological and laboratory approaches. Studies I-III used a data set consisting of small intestinal biopsy reports. The biopsies were taken in 1969-2008 and collected in 2006-2008. A total of 29,096 individuals with CD, 13,306 with inflammation and 3,719 with potential CD were identified. Each individual was matched with up to 5 controls from the general population (n= 228,632). Through linkage of the data to the Patient Register study I examined the risk of hospital visits due to respiratory syncytial virus (RSV) in children <2 years prior to onset of CD. Study II used the Patient Register and Cause of Death Register to assess whether CD affects the outcome in sepsis. Study III linked the data to microbiological data bases and the Public Health Agency to estimate risk of invasive pneumococcal disease (IPD) in CD. In study IV children with CD and controls were recruited from Kalmar County Hospital. Complement activation (C3a and sC5b-9) in plasma were analysed after incubation with pneumococci.

Results: Study I found that children with CD were more likely than controls to have attended hospital due to RSV infection prior to diagnosis (odds ratio 1.46; 95% confidence interval (CI)=1.02-2.07). CD did not seem to influence survival in sepsis (adjusted hazard ratio (HR) 1.10 95%CI=0.72-1.69) (study II). Study III indicated a 46% risk increase for individuals with CD to acquire IPD (HR 1.46; 95%CI=1.05-2.03) but study IV did not reveal any differences in complement response in regard to CD status (p=0.497and p=0.724), explaining this excess risk.

Conclusion: This thesis supports associations between CD and infections preceding and complicating diagnosis. However, CD does not seem to influence the outcome in a severe infection like sepsis and altered complement function is unlikely to be responsible for the excess IPD risk in CD.