Measurements of serum IgA and IgG activities to dietary antigens. A prospective study of the diagnostic usefulness in adult coeliac disease.

Serum samples from 458 consecutive adult patients with intestinal symptoms and/or suspected food intolerance were examined for IgG and IgA antibody activities to gluten, egg, and cow's milk antigens by an enzyme-linked immunosorbent assay (ELISA). Increased IgA and/or IgG activities to gluten were seen in 61 patients: 35 had coeliac disease (CD) as suggested by jejunal villous atrophy and subsequent histologic and/or clinical improvement on a gluten-free diet; 4 were previously diagnosed CD patients with clinically suspected dietary failure; 2 had dermatitis herpetiformis with a CD-like intestinal morphology; and 3 had possible gluten intolerance without villous atrophy. The rest had other disorders that might have affected the permeability of the gastrointestinal mucosa or the hepatic IgA catabolism. When the IgA activity to gluten was increased, neither the IgA/IgG activities to nongluten antigens nor the ratio of nongluten to gluten antibodies could discriminate between CD patients and those without CD. However, the median IgA activity to gluten was significantly higher in the CD group. The probability for CD thus increased from 33% in patients with IgA activity to gluten between 0.4 and 0.8 OD units to 90% in those with such activity above 2.4 OD units. Nevertheless, seven untreated CD patients had IgG and IgA activities to gluten within the normal range. ELISA determinations of serum antibodies to gluten antigens are a valuable adjunct in the diagnosis of adult CD, but a negative test does not exclude this disorder.