Clinical Information

Clinical Indications

• Supporting the evaluation of patients in whom celiac disease is suspected based on gastrointestinal symptoms, extraintestinal findings, or increased clinical risk
• Assessment of patients with associated autoimmune or genetic conditions known to increase the likelihood of celiac disease
• Adjunctive testing in individuals with selective IgA deficiency
• Following serologic trends in patients with established celiac disease who are undergoing dietary management

Clinical Background

Celiac disease is an immune-mediated disorder triggered by dietary gluten in genetically predisposed individuals. Exposure to gluten-containing grains (wheat, barley, and rye) results in inflammation of the small intestinal mucosa and varying degrees of villous atrophy, leading to impaired nutrient absorption.

Clinical presentation varies widely. Gastrointestinal manifestations may include chronic diarrhea, bloating, abdominal discomfort, or malabsorption. However, many patients present with extraintestinal findings such as iron deficiency anemia, decreased bone mineral density, delayed growth, infertility, neurologic symptoms, dermatitis herpetiformis, or nonspecific fatigue. The condition is more frequently observed in individuals with autoimmune disorders (e.g., type 1 diabetes or autoimmune thyroid disease), chromosomal conditions such as Down syndrome, and selective IgA deficiency.

Genetic predisposition is strongly linked to the presence of HLA-DQ2 and/or HLA-DQ8 haplotypes. While these markers are present in the vast majority of affected individuals, they are also common in the general population; therefore, their presence supports susceptibility but does not establish the diagnosis. HLA testing may be useful in selected situations, particularly when serologic and histologic findings are inconclusive or when testing is performed after initiation of a gluten-free diet.

Definitive diagnosis traditionally relies on small intestinal biopsy demonstrating characteristic histopathologic changes. Because biopsy requires endoscopic sampling, serologic assays are commonly used as a noninvasive screening and risk stratification tool. Antibodies associated with celiac disease include tissue transglutaminase (tTG), endomysial antibodies, and antibodies directed against deamidated gliadin peptides.

Deamidated gliadin antibody testing may be helpful in specific clinical settings, particularly in patients with IgA deficiency, where IgG-based assays play an important role. In individuals with normal total IgA levels, tTG IgA remains the preferred initial screening test due to its overall performance characteristics.

For accurate interpretation, serologic evaluation should be performed while the patient is consuming a gluten-containing diet. Antibody levels generally decrease following adherence to a gluten-free diet. Persistently elevated results may indicate ongoing gluten exposure or, less commonly, refractory disease.

Reference Intervals

Negative: <20.0 U

Weak positive: 20.0–30.0 U

Positive: >30.0 U

Reference values apply to all ages.

Result Interpretation

• Detection of deamidated gliadin IgA and/or IgG antibodies supports an immune response to gluten and may be seen in patients with celiac disease. Results should be interpreted in the context of clinical presentation and additional laboratory findings.
• Antibody concentrations below the assay cutoff reduce the likelihood of active celiac disease, although negative results do not completely exclude the diagnosis in all clinical scenarios.
• In patients who initiate a gluten-restricted diet, antibody levels may gradually decline over time. A downward trend can reflect adherence to dietary therapy.

Important Considerations and Limitations

Diagnostic Use

• Serologic testing alone is insufficient to establish or exclude celiac disease. These assays are best used to identify individuals who warrant further evaluation, which may include small intestinal biopsy.
• Testing should be performed while the patient is consuming a gluten-containing diet. Removal of gluten prior to testing may result in falsely low or negative antibody levels.
• If serologic results are negative but symptoms strongly suggest malabsorption or celiac disease, additional diagnostic evaluation, including endoscopic biopsy, should be considered. Several gastrointestinal disorders can mimic celiac disease clinically.

IgA Deficiency

• Selective IgA deficiency is more common in individuals with celiac disease and may lead to false-negative IgA-based results. If IgA deficiency is suspected, total IgA measurement and IgG-based testing should be considered.
• In patients with normal total IgA and negative IgA deamidated gliadin antibodies, the probability of active celiac disease is reduced; however, clinical judgment remains essential.

Specificity and Potential False Positives

• Elevated gliadin antibodies may occasionally be detected in conditions other than celiac disease, including certain inflammatory bowel disorders, food protein intolerance, and post-infectious gastrointestinal syndromes.
• Dermatitis herpetiformis is strongly associated with gluten-sensitive enteropathy. In these patients, antibody testing may assist in identifying intestinal involvement, even when gastrointestinal symptoms are minimal.

Assay-Related Considerations

• Results generated by this assay platform are method-specific. Antibody values from different manufacturers or methodologies are not interchangeable, and quantitative values should not be interpreted as equivalent to endpoint results.
• Results should always be evaluated alongside clinical findings and other relevant serologic markers, such as tissue transglutaminase antibodies.
• Performance characteristics have been validated for serum specimens only.

Additional Guidance

• Testing for antibodies against native (non-deamidated) gliadin proteins is no longer recommended due to limited diagnostic performance compared with modern serologic markers.
• This assay is not intended to replace tissue transglutaminase antibody testing, which remains the preferred initial serologic evaluation in most patients with sufficient total IgA.