Diagnosis of coeliac disease

Rubio-Tapia, 2013 Bai, 2017 Tye-Din, 2015

Coeliac serology testing can be used to assess for coeliac disease if the patient is consuming 8 to 10 grams of gluten per day (equivalent to 4 slices of wheat-based bread)Coeliac Australia Limited—it cannot be used in people on a gluten-free dietRubio-Tapia, 2013. Perform the following tests:

• immunoglobulin A (IgA) anti–tissue transglutaminase and anti–deamidated gliadin antibodies, which are highly sensitive and specific for coeliac disease
• total IgA should also be measured to exclude coeliac disease–associated IgA deficiency, which can cause false-negative antibody tests.

If coeliac serology is positive, arrange an endoscopic biopsy of the duodenal mucosa. The diagnosis of coeliac disease is confirmed by typical pathology—intra-epithelial lymphocytosis with blunting of duodenal villi.

Gene (HLA DQ2 and HLA DQ8) testing is not an appropriate screening test for coeliac disease. These genes are common, being present in approximately 50% of the Australian populationWalker, 2017. However, gene testing may be used in patients who have symptoms suggestive of coeliac disease (eg bloating) who are already on a gluten-free diet and are unwilling to expose themselves to gluten for a 4 to 6 week period in order to have serological testingBai, 2017. Coeliac disease cannot be diagnosed by the presence of HLA DQ2 or DQ8 alone; however, it can be excluded if gene testing is negativeBai, 2017Rubio-Tapia, 2013.