Identifying immunoglobulin-A--deficient children and adults does not necessarily help the serologic diagnosis of coeliac disease.

BACKGROUND: Immunoglobulin A deficiency is more common in patients with coeliac disease and also in patients with other gastrointestinal diseases than in normal people. There is a concern, therefore, that routine serum immunoglobulin (Ig) A testing of all cases of suspected coeliac disease may lead to unnecessary biopsy.
METHODS: Four hundred eighty-two routine consecutive samples from cases of suspected coeliac disease or malabsorption (109 children) were tested for IgA anti-endomysium and total IgA. Four hundred twenty-four sera samples also had IgG antigliadin checked for high-titre antibody. Archived adult sera from 31 patients with coeliac disease and 52 disease control subjects were included in the study.
RESULTS: Seven routine cases with serum IgA less than 15% of the mean normal for age and four cases with undetectable IgA were identified. Four patients, including three of four with clear deficiency, underwent small bowel biopsy, and all four had normal histologic findings and normal intraepithelial lymphocyte counts. Only one of the seven had high-titre IgG antigliadin antibody but that patient had normal histologic findings. One (3%) of 31 adults with established coeliac disease and 1 (2%) of 52 control subjects were IgA deficient.
CONCLUSIONS: Of patients with IgA deficiency, only those with both IgA deficiency and high-titre IgG antigliadin antibody should be routinely considered for biopsy.