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Editor,—I read Dr Metcalf’s recent commentary (Gut1998;42:9–10) on the association between coeliac disease and primary biliary cirrhosis, with much enthusiasm. Her editorial was both succinct and insightful. My concern relates to the author’s suggestion that for coeliac disease, “endoscopic small bowel biopsy is specific.” Unfortunately, this statement is incorrect. Specifically, a mucosal lesion identical to or closely resembling coeliac disease may be seen in patients with tropical sprue, lymphoma of the small bowel, Zollinger–Ellison syndrome, Crohn’s disease, bacterial overgrowth in the small intestine, as well as multiple other disorders.1 It is for this reason that it has been stressed that the histological appearance of the mucosa in coeliac disease is not specific, and alone cannot be considered diagnostic of this disorder. Importantly, in addition to a biopsy specimen showing the “typical” coeliac sprue lesion, a clinical response to gluten withdrawal is required to diagnose the disorder unequivocally.
Editor,—I thank Dr Yarze for his interest and kind comments. He is of course correct that small bowel biopsy is not 100% specific for coeliac disease taken in isolation. (Very few tests reach 100% specificity.) However, I hope he would agree that, in conjunction with a positive anti-gliaden antibody used as the intial screening test, the specificity is high. Another way of looking at this would be the positive predictive value of a small bowel biopsy, which depends upon the prevalence of the disease in the population being studied. As coeliac disease is relatively common among the Caucasian population affected by primary biliary cirrhosis, whereas the other cases of villous atrophy are rare among this group, small bowel biopsy would have a high positive predictive value.