To reduce the risk of missing IgA deficient patients, a Total IgA will be run for all low Tissue Transglutaminase IgA results. If IgA deficiency is identified, a reflex deamidated Gliadin IgG will be carried out to determine whether the patient is likely to have coeliac disease. Coeliac pathway: Initial TTG IgA samples are received and tested If TTG IgA is LOW <0.2 U/ml reflex testing for Total IgA will be undertaken If Total IgA is LOW /= 10 U/ml then reflex testing for Endomysial IgA will be undertaken as a confirmatory test for first time positive samples.