From the Guidelines
Blood tests for celiac disease include tissue transglutaminase antibody (tTGA), endomysial antibody (EMA), and deamidated gliadin peptide (DGP) tests, which are essential for diagnosing this autoimmune condition. The tTGA test is typically the first-line screening tool due to its high sensitivity and specificity, measuring antibodies against the tissue transglutaminase enzyme that becomes a target in celiac disease 1. The EMA test detects antibodies against the endomysium, a connective tissue around smooth muscle, and is highly specific but more technically demanding and expensive. The DGP test measures antibodies against modified gluten proteins and is particularly useful for patients with IgA deficiency or children under two years old.
Key Points to Consider
- These tests should be performed while the patient is on a gluten-containing diet, as eliminating gluten before testing can lead to false-negative results 1.
- A positive blood test typically requires confirmation with an intestinal biopsy for definitive diagnosis.
- The immune system produces antibodies against gluten and self-proteins in celiac disease, which can be detected in the bloodstream, reflecting the underlying autoimmune process triggered by gluten exposure 1.
- The tTGA test has high sensitivity (93%) and specificity (98%), making it a reliable first-line screening tool 1.
Diagnostic Approach
The diagnostic approach to detecting celiac disease involves serologic tests, particularly the IgA antiendomysial antibody (EMA) and the IgA tTGA, which have become a relatively sensitive and specific way to initially detect celiac disease 1. The IgA tTGA is both sensitive and specific for celiac disease and supplants the use of gliadin antibody testing as the preferred means of serologic detection.
Recommendations
The tTGA test is recommended as the first-line screening tool for celiac disease due to its high sensitivity and specificity. The EMA test and DGP test can be used as secondary tests or in specific situations, such as IgA deficiency or in children under two years old. Intestinal biopsy is still necessary for definitive diagnosis in most cases.
From the Research
Blood Tests for Celiac Disease
The following blood tests are used to diagnose celiac disease:
- Tissue transglutaminase antibody (tTGA) test: This test measures the level of antibodies against tissue transglutaminase, an enzyme found in the small intestine 2.
- Endomysial antibody (EMA) test: This test measures the level of antibodies against endomysium, a protein found in the small intestine 2.
- Deamidated gliadin peptide (DGP) test: This test measures the level of antibodies against deamidated gliadin peptides, which are found in wheat, barley, and rye 3, 4.
Sensitivity and Specificity of Blood Tests
The sensitivity and specificity of these blood tests vary:
- tTGA test: High sensitivity (100%) and specificity (94%) in diagnosing celiac disease 2.
- EMA test: High sensitivity (100%) and specificity (100%) in diagnosing celiac disease, but lower sensitivity (80%) in some studies 2, 3.
- DGP test: High sensitivity (91-94%) and specificity (85-98%) in diagnosing celiac disease 3, 4.
Combination of Blood Tests
Combining multiple blood tests can improve diagnostic accuracy:
- Combination of tTGA and DGP tests: Offers the best sensitivity without loss of specificity in diagnosing celiac disease 3.
- Combination of EMA and tTGA tests: Can be used to monitor patients with celiac disease on a gluten-free diet, but may not detect all cases of persistent villous atrophy 5.
Clinical Guidelines
Clinical guidelines recommend the use of these blood tests in the diagnosis and management of celiac disease:
- American College of Gastroenterology guidelines: Recommend the use of tTGA and EMA tests in the initial screening of patients with suspected celiac disease, and intestinal biopsy to confirm the diagnosis 6.
- Other guidelines: Recommend the use of DGP test as an additional diagnostic tool, especially in patients with persistent symptoms despite a gluten-free diet 4.