Coeliac disease: to screen or not to screen, that is the question.

An appropriate strategy is to test patients with symptoms and signs attributable to coeliac disease n recent years, knowledge about coeliac disease (CD) has improved significantly, and we now have a better understanding of the diagnosis and pathogenesis of the disease. In this issue of the Journal on page 429, Chin and colleagues report the largest community study of CD undertaken in Australia. 1 The study found a prevalence of CD of between 0.56% and 0.96%, 1 similar to prevalences found in European population studies. A recent population-based serological study (without biopsy) in the United States found a prevalence of 0.95%. 2 The screening strategy used by Chin and colleagues involved IgA and IgG anti-tissue transglutaminase (anti-tTG) antibody assays, HLA-DQ2 and HLA-DQ8 haplotyping, and, where appropriate , gastroscopy and duodenal biopsy. 1 We believe that the data do not justify population-based screening for CD in Australia, but the diagnostic approach developed by Chin et al is appropriate for diagnosing patients in whom CD is suspected. Genetic and environmental factors are important in the genesis of the disease. The role of the HLA-DQ2 and-DQ8 haplotypes is yet to be fully understood. One or other haplotype is present in nearly all CD patients, yet they are also present in 20%–40% of subjects without CD. The " gold standard " for diagnosis has long been histological findings from a duodenal biopsy, despite the discordance between clinical symptoms and these findings. CD is caused by an immune response to antigens in gluten proteins. Wheat, barley and rye, but not corn or rice, contain gluten proteins. Ingested gluten is partially digested to peptides, some of which are absorbed into the lamina propria of the small intestine. The enzyme, tissue transglutaminase, deamidates certain glutamine residues in the peptides to glutamic acid. In patients with CD, this results in enhanced binding to HLA-DQ2 or-DQ8 cells. Within the lamina propria, T cell recognition of the amino acid sequences presented by the DQ2 or DQ8 cells produces a series of inflammatory changes, with the release of cytokines and the activation of lymphocytes. This leads to the characteristic histological findings in the proximal duodenum — lymphocytic infiltration, villous damage or loss, and crypt hyperplasia. 3 Increases in transglutaminases in the lamina propria produce several effects: they catalyse the crosslinking of gluten peptide residues to lysine residues in various local proteins, including in transglutaminase itself, creating an immunogenic gluten–peptide– protein complex. …