Celiac disease

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Celiac disease can present in many varied ways and requires a high degree of clinical suspicion.

Presenting features

Patients with unexplained gastrointestinal symptoms (including those diagnosed with irritable bowel syndrome and/or dyspepsia), chronic diarrhea, unexplained iron deficiency anemia, or a skin rash consistent with dermatitis herpetiformis should be tested for celiac disease.[64][65][66]

Other situations that may prompt testing include failure to thrive, short stature, vitamin deficiency (B12, D, or folate), recurrent severe aphthous stomatitis, recurrent spontaneous abortion, and infertility.[67]

Investigations

Before testing, it is crucial to ensure that the patient is ingesting gluten, because all diagnostic tests will usually normalize on a gluten-free diet.

1. Serology

Immunoglobulin A-tissue transglutaminase (IgA-tTG) titer should be evaluated as the initial test.[34][68][69][70][71][72]
Quantitative IgA is often routinely requested to assess for IgA deficiency, as the presence of IgA deficiency renders IgA-tTG insensitive. IgA deficiency is more common in people with celiac disease than in the general population.[73]
Endomysial antibody (EMA) is a more expensive alternative to IgA-tTG, with greater specificity but lower sensitivity, which may be used if IgA-tTG is unavailable.[74] Unlike tTG, which is an enzyme-linked immunosorbent assay, EMA is based on immunofluorescence and thus is operator dependent.
In patients with IgA deficiency, request IgG-deamidated gliadin peptide (DGP) serology, although the diagnostic accuracy of this test is somewhat less than that of IgA-tTG.[69][75] DGP serology has largely replaced IgG-tTG serology for IgA-deficient patients. DGP and IgG-tTG serology should not be used as initial investigations ahead of IgA-tTG and quantitative IgA assessment.[34][70][71][72]
In children ages <2 years who do not have IgA deficiency, IgA-TTG is the preferred test to confirm celiac disease diagnosis, whereas in those with IgA deficiency, IgG-DGP or IgG-tTG can be used as confirmatory tests.[70][76]
Patients with an elevated IgA-tTG level should be advised to remain on a gluten-containing diet and referred for duodenal biopsy.
A normal IgA-tTG and total IgA test result are adequate to exclude a diagnosis in patients with a low clinical index of suspicion for celiac disease.[70]
In an individual with a high clinical index of suspicion for celiac disease, it is reasonable to proceed with esophagogastroduodenoscopy and duodenal biopsy even in the face of normal serologies.[70]

2. Histology

Patients with an elevated IgA-tTG level should be advised to remain on a gluten-containing diet and referred for duodenal biopsy.
Small intestinal biopsies should be obtained regardless of the IgA-tTG result in patients with a high clinical index of suspicion, as 2% of patients with celiac disease may not have circulating tTG at the time of diagnosis (seronegative celiac disease).[77]
Pediatric patients with symptoms consistent with celiac disease and a high IgA-tTG titer (above 10 times normal range for laboratory) may go on to have confirmatory EMA testing. If EMA is positive, celiac disease may be diagnosed without a small intestinal biopsy.[78]
Some experts advise that adult patients with very high IgA-tTG titers (above 10 times the normal range for laboratory), and positive EMA in a second blood sample, may be diagnosed without duodenal biopsy.[71] These criteria may be considered an “after the fact” diagnosis among adults unwilling or unable to undergo duodenal biopsy.[70]
Duodenal biopsy changes in celiac disease are typically graded by the Marsh-Oberhuber classification, from 0 to 4.[79] To diagnose celiac disease, intraepithelial lymphocytes should be increased and the villous-to-crypt ratio decreased. The presence of only one of these changes raises the possibility of a different diagnosis.[Figure caption and citation for the preceding image starts]: Histologic image of small intestinal villous atrophy and crypt hyperplasiaFrom the personal collection of DA Leffler; used with permission [Citation ends].
The presence of typical celiac changes on duodenal histology with clinical improvement on a gluten-free diet confirms the diagnosis. A repeat duodenal biopsy after gluten withdrawal is no longer routinely necessary for verification.[Figure caption and citation for the preceding image starts]: Histologic image of small intestinal villi showing resolution of intestinal injury on gluten-free dietFrom the personal collection of DA Leffler; used with permission [Citation ends].[Figure caption and citation for the preceding image starts]: Photograph of small intestinal villi affected by celiac diseaseFrom the personal collection of DA Leffler; used with permission [Citation ends].[Figure caption and citation for the preceding image starts]: Photograph of normal small intestinal villiFrom the personal collection of DA Leffler; used with permission [Citation ends].[Figure caption and citation for the preceding image starts]: Capsule endoscopy pictures of ulcerative jejunitis in a patient with celiac diseaseFrom the personal collection of Amelie Therrien; used with permission [Citation ends].

3. Human leukocyte antigen (HLA) typing

May be used to rule out celiac disease in patients already on a gluten-free diet or in patients with an idiopathic celiac-like enteropathy, but is only helpful for diagnosis in select cases, such as when there is discrepancy between serologic and histologic findings.[70]
HLA typing may be used as a first-line screening test to rule out celiac disease among first-degree relatives.[34] However, the availability and cost of this test in this context may be prohibitive.

4. Endoscopy

Atrophy and scalloping of mucosal folds; nodularity and mosaic pattern of mucosa may be seen, but these findings are neither sensitive nor specific for celiac disease diagnosis. [Figure caption and citation for the preceding image starts]: Scalloping of the duodenal mucosa in a patient with celiac diseaseFrom the personal collection of DA Leffler; used with permission [Citation ends].[Figure caption and citation for the preceding image starts]: Scalloping of the duodenal mucosa in a patient with celiac diseaseFrom the personal collection of DA Leffler; used with permission [Citation ends].
Video capsule endoscopy enables imaging of the entire small intestine and has good sensitivity for the detection of macroscopic features of celiac disease. Capsule endoscopy is, however, typically used to detect complications of celiac disease, such as ulcerative jejunitis or lymphoma.[80][81]

Gluten challenge

People with celiac disease on a gluten-free diet prior to evaluation cannot be differentiated from healthy controls. In these patients, gluten challenge is necessary. In a gluten challenge, the person is placed back on a gluten-containing diet, containing 3-10 grams of gluten per day (2-5 slices of wheat bread), with serologic tests and small bowel histology assessed after 2-8 weeks on the gluten-containing diet.[82][83]

Commercial kits

Patients who have used a home-testing kit, or are considering using one, should be counseled to discuss their symptoms with their healthcare professional, irrespective of the test outcome.

Commercially available tests for the assessment of individual risk for celiac disease detect the presence of HLA-DQ2 and HLA-DQ8 genes in saliva.[84]

Healthcare professionals should be aware that patients who test positive for tTG antibodies using self-administered blood tests (finger-prick tests) may begin a gluten-free diet before being evaluated by their healthcare professional, and this may make subsequent diagnostic workup difficult.[85]

Tests for detection of tTG antibodies in saliva are being investigated, but there is insufficient evidence to recommend their use.[34]

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