Diagnosis of coeliac disease in children in primary care and clinical implications.

Since the introduction of the Crosby capsule (a device used for obtaining biopsies of small bowel mucosa, necessary for the diagnosis of various small bowel diseases) in the 1970s, small intestinal biopsy has been the cornerstone of diagnosis of coeliac disease. In paediatric practice, successive position statements from the European Society of Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) have defined criteria for childhood diagnosis: initially based on three successive biopsies at presentation, on a gluten-free diet, and then challenge. Since 1990, the diagnosis has been dependent on a single biopsy with a clear clinical response to a gluten-free diet, supported by positive serology. 1 This approach is similar to that recommended for adults 2 and has been adopted by the National Institute for Health and Care Excellence (NICE). 3 advances in understanding Great strides have been made in serological assessment and understanding coeliac disease pathogenesis since the 1990 guidelines were introduced. First, the non-specific gliadin antibodies used at that time were supplanted by the highly specific IgA endomyseal antibody (EMA) test. Subsequently tissue transglutaminase-2 (tTG) was identified as the true autoantigen causing EMA reactivity. EMA testing depends on immunofluorescence, giving a yes–no answer dependent on operator expertise. Importantly, assay of tTG autoantibody is performed by enzyme-linked immunosorbent assay (ELISA), allowing a quantitative assessment of immune response. The second major diagnostic advance was the determination of the relevant human leukocyte antigen (HLA) types that allow presentation of gliadin/ tTG complexes to T cells, thus causing the autoimmune response to tTG. Persons of tissue types HLA-DQ2 and HLA-DQ8 (more than a quarter of the UK population) make up 99% of cases of coeliac disease, and true coeliac disease is very unusual in someone who is not DQ2 or DQ8 positive. 4 coeliac disease: a common disorder The widespread introduction of EMA and tTG testing for coeliac disease led to recognition that the disease is much more common than previously thought; affecting about 1% of the population. There has therefore been a shift towards recognition of people with more subtle symptoms, but even now around 80% of cases remain unrecognised in both adults and children compared with what would be expected in a screening programme. 5 The long-term consequences of truly asymptomatic coeliac disease are unknown, and, as such, population screening is not yet indicated. However, the challenge is to identify people with active coeliac disease but relatively subtle symptoms. Symptoms that should …