Coeliac disease

Coeliac disease is an autoimmune enteropathy triggered by dietary gluten. For information on HLA typing for coeliac disease, click here.

Diagnostic serology for coeliac disease performs relatively well, with sensitivity and specificity in excess of 90%. Please note the following:
 

1. The tests are only valid if the patient is taking a gluten-containing diet. Patients should take gluten in most meals every day for six weeks before testing. Testing in infants should be deferred until they have been weaned and are taking gluten.

2. Endomysial and TTG antibodies are of IgA isotype. False negatives occur if the patient is IgA-deficient. We now use a screening assay to detect possible low-IgA sera, and will only formally quantify IgA where indicated. IgG coeliac serology will be automatically performed when IgA levels are low.

3. In case of positive serology, a small bowel biopsy whilst taking a gluten-containing diet is required for initial confirmation of the diagnosis.

4. Serology may occasionally be negative in affected patients, as the sensitivity is not 100%. Small bowel biopsy should be considered if the clinical features are highly suggestive.

 

Alternative names, keywords

Endomysial antibody, EMA, tissue transglutaminase antibody, TTG antibody, anti TTG

Samples required

Clotted blood (gold cap, 5 mL tube). Smaller tubes are available for paediatric samples.

Test indications

Suspected coeliac disease.

Test information

Samples are screened by IgA TTG antibody. All positive samples will be tested for IgA endomysial antibody by indirect immunofluorescence.

Reference range

EMA reported as positive or negative

TTG antibody: <20 negative, 20-30 weak positive, >30 positive

Strong positive IgA TTG results with positive endomysial staining has high predictive value for coeliac disease. The predictive value of weak positive TTG antibody results is lower, particularly when endomysial staining is absent.

Turnaround time

Tests are performed twice a week, turnaround time 7 days.

Enquiries

Immunology