The First Step:
tTG-IgA Test
For most children and adults, the best way to test for celiac disease is with the Tissue Transglutaminase IgA antibody (tTG-IgA), plus an IgA antibody in order to ensure that the patient generates enough of this antibody to render the celiac disease test accurate.
For young children (around age 2 years or below), Deamidated Gliadin IgA and IgG antibodies should also be included. All celiac disease blood tests require that you be on a gluten-containing diet to be accurate. The tTG-IgA test will be positive in about 93% of patients with celiac disease who are on a gluten-containing diet. This refers to the test’s sensitivity, which measures how correctly it identifies those with the disease. The same test will come back negative in about 96% of healthy people without celiac disease. This is the test’s specificity. ,
There is also a slight risk of a false positive test result, especially for people with associated autoimmune disorders like type 1 diabetes, autoimmune liver disease, Hashimoto’s thyroiditis, psoriatic or rheumatoid arthritis, and heart failure, who do not have celiac disease.
There are other antibody tests available to double-check for potential false positives or false negatives, but because of potential for false antibody test results, a biopsy of the small intestine is the only way to diagnose celiac disease.
For patients ages 18+, one available test is Proud Sponsor Labcorp OnDemand’s Celiac Disease Antibody Test, which measures tTG-IgA and total IgA. If your total IgA level is low, testing for tTG-IgG and DGP-IgG will be performed.
Other Tests
IgA Endomysial antibody (EMA): The EMA test has a specificity of almost 100%, making it the most specific test for celiac disease, although it is not as sensitive as the tTG-IgA test. About 5-10% of people with celiac disease do not have a positive EMA test. It is also very expensive in comparison to the tTG-IgA and requires the use of primate esophagus or human umbilical cord. It is usually reserved for difficult to diagnose patients.
Total serum IgA: This test is used to check for IgA deficiency, a condition associated with celiac disease that can cause a false negative tTG-IgA or EMA result. If you are IgA deficient, your doctor can order a DGP or tTG-IgG test.
Celiac Disease Antibody Test: This test from Proud Sponsor Labcorp OnDemand measures tTG-IgA and total IgA for patients ages 18+. If your IgA level is low, testing for tTG-IgG and DGP-IgG will be performed.
Deamidated gliadin peptide (DGP IgA and IgG): This test can be used to further screen for celiac disease in individuals with IgA deficiency, which affects 2-3% of patients with celiac disease, or people who test negative for tTg or EMA antibodies. IgA deficiency in a patient may be indicative of other diseases that may cause villus atrophy, such as giardiasis, small-bowel bacterial overgrowth (SIBO) or common variable immunodeficiency (CVID).
While it is very rare, it is possible for someone with celiac disease to have negative antibody test results. If your tests were negative, but you continue to experience symptoms, consult your physician and undergo further medical evaluation.
Video capsule endoscopy (VCE): VCE has a sensitivity of 89% and specificity of 95% for celiac diagnosis. This method of testing is more sensitive at detecting macroscopic atrophies in comparison with regular upper endoscopy (92% vs. 55%). VCE is also useful in detecting complications linked with celiac disease.
Intestinal fatty acid binding protein (I-FABP): When cellular damage occurs, this cytosolic protein is released into the systemic circulation of blood and could indicate unintentional gluten intake.
Radiology: Some radiological findings may indicate the presence of celiac disease, e.g., small-bowel dilation, wall thickening, vascular changes, and others.
Who should have Celiac HLA testing?
Those on a gluten-free diet – celiac antibody blood testing is not accurate
- when diagnosis of celiac disease is not clear
- ambiguous antibody testing results (especially in children under the age of 3)
- equivocal intestinal biopsy results
- discrepancy between antibody and biopsy findings
- family members of people with celiac disease to evaluate risk
- a negative result assures a 99% probability that the family member will NOT develop celiac disease
- a positive result indicates the family member should follow up with celiac antibody testing every 2-3 years or immediately if symptoms develop
