Evaluation for celiac disease in a child who is already on a gluten-free diet

tTG-IgA: IgA antibodies to tissue transglutaminase; IgA: immunoglobulin A; HLA: human leukocyte antigen; DGP: deamidated gliadin peptide; IgG: immunoglobulin G.

* For children <5 years who are already on a gluten-free diet, options depend on the severity of the child's presenting symptoms and duration of a gluten-free diet. For most such children, we perform serologic screening (tTG-IgA and total IgA). If the result is positive, we interpret as for children on a gluten-containing diet. If the result is negative, we generally avoid a gluten challenge because young children may not be able to verbalize their symptoms. We advise continuing the gluten-free diet until the child is at least 5 years of age, then proceeding to a gluten challenge if the family is willing to do so.

¶ Total IgA below the normal range indicates IgA deficiency, which is present in approximately 2% of patients with celiac disease. For these patients, the appropriate test for celiac disease is tTG-IgG, in combination with DGP-IgG (rather than IgA-based tests).

Δ HLA-DQ2 or DQ8 serotypes are present in virtually all patients with celiac disease but are also common in the general population. Hence, HLA testing is only useful for ruling out celiac disease; a positive result is not informative.