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Letter: the end of duodenal biopsies in coeliac disease? Authors’ reply

EDITORS, We thank Drs. Scicluna and Ellul for their important remarks regarding our paper. We fully agree that the difference in kinetics and cut offs of commercial tissue transglutaminase (tTG)‐based tests is a major challenge with the serology‐based criteria. Promisingly, Werkstetter et al recently showed in a large multi‐centre paediatric study that tTG‐IgA >10× ULN had 99% positive predictive value for coeliac disease with eight commonly used tTG‐IgA kits. There are, however, also many more assays in the market for which accuracy in these circumstances should be confirmed. In fact, the lack of standardization is one the main reasons for the current requirement of the rather high cut off for the serological approach. Another important issue that the commentators brought out is the role of the more laborious endomysial antibody (EMA) in the revised diagnostic approach. It is true that, as seen also in the present study, there is an excellent concordance between high tTG‐ab levels and EmA positivity. Once again, though, the lack of standardization and variable kinetics of the tTG‐based tests underlines the role of EmA as quality control for the correctness of coeliac disease diagnosis in all settings. On the contrary, the necessity for HLA testing can be questioned, as it has low positive predictive value for coeliac disease and does not seem to add much to the diagnostic accuracy. Therefore, genetic testing should be utilized mainly with unclear cases as an exclusion tool. As the authors say, omitting the requirement for HLA testing could provide substantial economic benefits without compromising diagnostic specificity. Of course, we must also remember that use of EmA and even HLA is still less expensive compared with endoscopy. Finally, Drs. Scicluna and Ellul reminded us of the clinicians ́ key role in correct implementation of the possible revised diagnostic criteria for coeliac disease. It is essential that all healthcare providers applying the non‐biopsy approach familiarize themselves with the performance and kinetics of the test kit they use, as well as ensure the existence of adequate laboratory quality control. Furthermore, local circumstances and possibilities for serological (EmA) testing should be carefully taken into account before such a major change in diagnosis of a life‐long disease is made.