Diagnostic approach for suspected celiac disease in an adult patient on gluten containing diet*

tTG: tissue transglutaminase; IgA: immunoglobulin A; DGP: deamidated gliadin peptide; IgG: immunoglobulin G; EMA: endomysial antibody; HLA: human leukocyte antigen.
* Testing for celiac disease should be performed in adults with suggestive gastrointestinal or extraintestinal signs/symptoms of celiac disease. Testing for celiac disease should ideally be performed while patients are on a gluten containing diet.
¶ The histologic severity of intestinal lesions in celiac disease are graded using the Marsh-Oberhuber classification. Marsh 2 and 3 are consistent with a diagnosis of celiac disease in individuals with positive celiac-specific serology. Marsh 1 is equivocal and Marsh 0 is normal. Refer to UpToDate content on the diagnosis of celiac disease.
Δ The intestinal biopsy should be reviewed by a pathologist familiar with celiac disease to look for subtle abnormalities of celiac disease.
◊ Absence of alleles encoding DQ2 or DQ8 excludes celiac disease.
§ Other conditions associated with lymphocytic duodenosis include Helicobacter pylori infection, medications (eg, non-steroidal antiinflammatory drugs), small bowel bacterial overgrowth, and systemic autoimmune disorders.
¥ Individuals with positive celiac-specific serology but Marsh 0 or 1 intestinal lesions on duodenal biopsy have potential celiac disease. Individuals with potential celiac disease should be evaluated and monitored further depending upon their clinical circumstances. Symptomatic patients with potential celiac disease are likely to benefit from treatment with a gluten free diet. Asymptomatic patients can remain on a normal diet unless clinical features of celiac disease develop.
‡ There are several causes of non-celiac enteropathy (villous atrophy in duodenum). Potential causes include giardiasis, small-bowel bacterial overgrowth, and common variable immunodeficiency. For a more comprehensive list of causes, refer to UpToDate content on diagnosis of celiac disease.
† An improvement in histology (with or without complete resolution) on a gluten free diet in patients with villous atrophy strongly supports a diagnosis of celiac disease.