Editor:

1. Editor: • Dr Mohammad Sadrkabir

2. Is there an association between coeliac disease and flammatory boweldiseases? A study of relative prevalence incomparison with populationcontrols Scandinavian Journal of Gastroenterology, 2007; 42: 12141220 JOHN S. LEEDS et al.

3. Introduction • Coeliac disease or gluten-sensitive enteropathy is a state of heightened immunological responsiveness to ingested gluten and is associated with the HLA DQ2 or DQ8 haplotype. • A number of screening studies have shown the prevalence of coeliac disease to be 1 in 100200 individuals. • Being of autoimmune origin, coeliac disease is associated with other autoimmune conditions such as type 1 diabetes mellitus , autoimmune thyroid disease , Addison’s disease and primary biliary Cirrhosis .

4. In recent years there have been reports on the prevalence of coeliac disease in inflammatory bowel diseases (IBD) . There are very few large studies in unselected cohorts investigating the coexistence of IBD and coeliac disease and those that have been published report a wide range of prevalence values and often conflicting results.(table 1) • The aim of this study was to establish the prevalence of coeliac disease in IBD and the prevalence of IBD in coeliac disease. Furthermore, local population prevalence rates of both coeliac disease and IBD were established.

6. Material and methods • At the Royal Hallamshire Hospital, Sheffield, UK, there are over 2000 patients registered as having IBD and over 400 registered as having coeliac disease. • The patients were only included in the study if the histology confirmed the diagnosis of IBD. • Demographic information was recorded, as was information on type of IBD, extent of disease and details of any immunosuppressant therapy received. • A blood sample was tested for IgA and IgGantigliadin antibodies, IgAendomysial antibodies, IgA anti-tissue transglutaminase antibodies and total IgA level. • Patients with any positive antibody (or combination of positive antibodies) or IgA deficiency were invited to undergo a distal duodenal biopsy.

7. Patients with coeliac disease were recruited from the specialist coeliac clinic. • Patients were included from two main groups: 1) those who had ever had a colonoscopy (80% of our cohort presented either with iron-deficiency anaemia or chronic diarrhoea), 2) those with persistent gastrointestinal symptoms despite being established on a gluten-free diet. • Local expertise in ileocolonoscopy ensures a high caecal intubation rate (90%) and terminal ileal intubation rate. • In those patients with normal macroscopic appearances, random colonic biopsies were taken to exclude microscopic colitis.

8. Control group • A total of 601 controls were recruited from five general practices in the South Yorkshire region. • Participants completed a validated questionnaire to determine gastrointestinal symptoms and diagnoses and provided blood samples to be tested for IgA and IgGantigliadin antibodies, IgAendomysial antibodies (EMAs) and total IgA level. • Participants with any positive antibody (or combination of positive antibodies) or IgA deficiency were invited to have a distal duodenal biopsy. Their case notes were reviewed to confirm a stated diagnosis of IBD.

9. Coeliac serological assays • IgG and IgAantigliadin antibodies were determined using ELISA. • EMAs were detected by indirect immunofluorescence using human umbilical cord as the substrate. • Anti-tissue transglutaminase antibodies were detected using ELISA and IgA level was determined using end-point nephelometry.

10. Distal duodenal biopsies • Four specimens were taken from the third part of the duodenum. • Histological features of coeliac disease were in concordance with the modified Marsh criteria with grade 3 or above changes being considered diagnostic of coeliac disease. • Approval was obtained from the South Sheffield Research Ethics Committee and written informed consent was received from each participant.

11. Statistical analysis • Data were analysed using SPSS version 13.0. Comparison of prevalence between disease groups and controls was performed using either the Fisher exact test or the x2 test; a p-value of less than 0.05 was considered to be statistically significant. A backwards, stepwise, logistic regression model was constructed in an attempt to identify clinical characteristics predictive of coexistent coeliac disease and IBD.

12. Results • A total of 1260 participants were enrolled in the study, of whom 354 patients (209 F, median age 45 years) had IBD (173 Crohn’s disease, 154 ulcerative colitis (UC), 18 indeterminate colitis and 9 microscopic colitis), 305 patients (222 F, median age 52 years) had coeliac disease and 601 were healthy controls (391 F, median age 47 years). • Patients in the coeliac disease group were significantly older than those in both the IBD group (pB0.0001) and the healthy controls (p0.002).

13. Prevalence of coeliac disease in IBD • We found that 307/354 (86.7%) patients had completely negative antibody screening tests and normal IgA levels; 2/354 (0.56%) had IgA deficiency, both of whom had normal duodenal biopsies.

14. 172 patients were receiving immunosuppressive therapy with azathioprine. There was no difference in antibody status between those on azathioprine and those not taking azathioprine (17/155 on azathioprine versus 26/156 not receiving azathioprine, the Fisher exact test p0.21). • All patients with subsequent villous atrophy were not taking azathioprine. However, patients who had previously received infliximab were more likely to have a positive anti-tissue transglutaminase antibody (4/24 received versus 15/330 without infliximab, the Fisher exact test p0.03). • Three patients (0.85%) were found to have villous atrophy on duodenal biopsy, two of whom had UC and one had Crohn’s disease.

15. One patient (Crohn’s disease) with positive EMA and anti-tissue transglutaminase antibody levels has so far declined to have a duodenal biopsy. • The prevalence of coeliac disease in this cohort was therefore 3/354 (0.85%) compared with 5/601 (0.83%) in the population control group (odds ratio 1.02, 95% CI, 0.24 - 4.29, p1.0).

16. Prevalence of IBD in coeliac disease • A total of 305 patients with coeliac disease were included in the study, all of whom had undergone ileocolonoscopy with colonic biopsies. • We found evidence of IBD in 10/305 (3.3%) patients;5 patients had lymphocytic colitis and 5 had UC. • In 9/10 patients the diagnosis of coeliac disease was made first and IBD identified during follow-up (Table III). The prevalence of IBD in the control group was 2/601 (0.33%) due to one case of UC and one case of Crohn’s disease.

18. The prevalence of IBD was much higher in the coeliac group (10/305, 3.3%) compared with the population control group (2/601, 0.33%) with an odds ratio of 9.98 (95% CI, 2.845.9, p0.0006). • If the microscopic colitis group were excluded, the prevalence of IBD would remain significantly higher (5/305 versus 2/601, odds ratio 4.99, 95% CI, 1.025.9, p0.046).

19. Multivariate analysis • Backwards stepwise logistic regression was performed using clinical variables in an attempt to identify factors likely to predict development of coeliac disease in patients with IBD. The variables used were age, gender, disease type (UC, Crohn’s, indeterminate colitis or microscopic colitis), extent of disease (colonic, small bowel only, ileocolonic, other), IgG and IgAantigliadin antibody status, EMA positivity and anti-tissue transglutaminase antibody titre. Only positive EMA or anti-tissue transglutaminase antibodies were found to be significant (pB0.0001).

20. Discussion • This is the first study to examine the prevalence of coeliac disease in IBD and IBD in coeliac disease compared with prevalence in local population controls. • We have shown that patients with coeliac disease have a 10-fold increased risk of developing IBD when compared with the general population. • In patients with IBD there was no increased risk of developing coeliac disease as compared to the general population, although this appears to be at variance with the findings of previous studies. • We found no cases of Crohn’s disease amongst those initially diagnosed with coeliac disease.

21. There have already been a number of publications investigating the relationship between coeliac disease and IBD . • Yang et al. [23] performed the largest study on coeliac disease looking for reports of IBD in 455 patients with biopsy-proven coeliac disease. They found that 27/455 (5.9%) patients had IBD (5 UC, 5 Crohn’s disease and 17 microscopic colitis). However, these investigators recognized that IBD may have been more frequent in their centre because of the specialized nature of their practice and a large local Jewish population. • Other studies of patients with refractory coeliac disease and persistent gastrointestinal symptoms despite commencement of a gluten-free diet also found concomitant IBD as a cause.

22. There have been a number of studies investigating, in particular, the relationship between coeliac disease and lymphocytic colitis. • Some investigators report a high prevalence of colonic lymphocytosis in patients with coeliac disease, which is indistinguishable from lymphocytic colitis, whereas one study identified differences between the lymphocytosis of untreated coeliac disease and that of lymphocytic colitis. • Increased prevalence of coeliac disease in lymphocytic colitis has also been described, leading to the suggestion that colonic lymphocytosis may be a colonic manifestation of coeliac disease.

23. Similarly, there are a number of studies investigating the prevalence of coeliac disease or celiacrelated antibodies in cohorts of patients with IBD. Owing to the small size of the IBD cohort in a number of these studies, the reported prevalence of coeliac disease has varied from 0.3% to 14%. • Falsepositive anti-tissue transglutaminase antibodies may be a phenomenon of autoimmunity. In many of these studies duodenal biopsies were not performed ubiquitously. Our data corroborate this view in that 16/354 (4.5%) patients had positive anti-tissue transglutaminase antibodies but negative EMAs but only one patient was found to have coeliac disease on biopsy. • Even though many centres no longer use antigliadin antibodies to screen for coeliac disease because of the perceived high falsepositive rate, they were included in this study to confirm the lack of specificity in this setting. On the basis of these results, our centre may withdraw this test.

24. Although coeliac disease and IBD do not share similar HLA haplotypes there may be other, as yet undetermined, genetic factors.Cottone et al. found an increased prevalence of UC in 1st-degree relatives of patients with coeliac disease. • Mucosal barrier defects are well described, such as increased tight junction permeability in both coeliac disease and IBD. Increased intestinal permeability may lead to increased antigen presentation and therefore generation of autoantibodies or increased bacterial translocation, which has been implicated in IBD as a pathogenic mechanism. • Pathogenesis of coeliac disease requires possession of either theDQ2 or the DQ8 allele and therefore increased gliadin presentation in IBD alone may not be a sufficient stimulus. This may explain why we found that IBD was more common in coeliac disease but not find an increase of coeliac disease in IBD.

25. Confounding factors • Interpretation of duodenal biopsy specimens is of key importance as there is the possibility of misdiagnosis, particularly in Crohn’s disease. A previous study on Crohn’s disease reported significant villous atrophy and increased intraepithelial lymphocytes in a number of patients. Serological testing was not performed in this study. All biopsy specimens were reviewed and grading was performed according to the modified Marsh grade. • Although microscopic colitis is not generally considered a classical inflammatory bowel disease, we have reported our findings as have other investigators. • The identification of IBD in patients with coeliac disease is a further confounding factor. Not all patients with coeliac disease undergo ileocolonoscopy at diagnosis owing to the mechanism of presentation. This suggests that the prevalence of IBD may be higher in patients with coeliac disease overall.

26. Conclusions • This is the first study to investigate the prevalence of coeliac disease in IBD and IBD in patients with coeliac disease in comparison with local population controls. • Patients with coeliac disease have an increased risk of developing IBD during follow-up, whereas patients with IBD have no increased risk of coeliac disease as compared with the background population. • Patients with coeliac disease and lower gastrointestinal symptoms or persistent anaemia should be offered colonoscopy and biopsy to exclude colitis. • The mechanisms behind this association need further investigation with particular reference to genetic markers and intestinal permeability.

27. Thank you for your attention