From the Guidelines
The primary blood tests used to diagnose celiac disease are serological antibody tests, specifically tissue transglutaminase antibody (tTG-IgA) and total serum IgA, as recommended by the most recent and highest quality study 1. The tTG-IgA test is the most sensitive and specific test, making it the preferred initial screening tool. If total IgA levels are low, additional tests like deamidated gliadin peptide antibodies (DGP IgG) or tTG-IgG may be needed since IgA-deficient patients might have false-negative results on standard tests. Other antibody tests sometimes used include endomysial antibody (EMA-IgA) tests, which are highly specific but more expensive and operator-dependent. These blood tests should be performed while the patient is on a gluten-containing diet, as following a gluten-free diet can lead to negative test results even in people with celiac disease. It's essential to note that while blood tests are excellent screening tools, a definitive diagnosis typically requires an intestinal biopsy to confirm intestinal damage characteristic of celiac disease, as supported by other studies 1. However, recent guidelines have begun to move towards biopsy-avoidance strategies for celiac disease in children and adults, as mentioned in 1. The tests work by detecting the immune system's abnormal response to gluten, which is the underlying mechanism of celiac disease. Key considerations in the diagnosis of celiac disease include:
- The patient's dietary history and current gluten intake
- The presence of symptoms or laboratory evidence of malabsorption
- The results of serological testing, including tTG-IgA and total serum IgA
- The need for intestinal biopsy to confirm the diagnosis in some cases
- The potential for false-negative results in IgA-deficient patients
- The importance of careful interpretation of test results and consideration of other potential causes of enteropathy, as discussed in 1. Overall, the diagnosis of celiac disease requires a comprehensive approach that incorporates clinical evaluation, serological testing, and intestinal biopsy, as appropriate.
From the Research
Blood Tests for Celiac Disease
The following blood tests are used to diagnose celiac disease:
- IgA antibodies to tissue transglutaminase (tTG) 2, 3, 4, 5, 6
- IgG antibodies to tissue transglutaminase (tTG) 2, 3, 4, 5, 6
- Endomysial antibodies (EMA) 2, 3, 4, 5
- Antigliadin antibodies (AGA) 2, 3, 4, 5
Sensitivity and Specificity of Blood Tests
The sensitivity and specificity of these blood tests vary:
- IgA anti-tTG: sensitivity 92-100%, specificity 98-100% 2, 3, 4, 5, 6
- IgG anti-tTG: sensitivity 21-100%, specificity 97-100% 2, 3, 4, 5, 6
- EMA: sensitivity 94-100%, specificity 100% 2, 3, 4, 5
- AGA: sensitivity 74-96%, specificity 97% 2, 3, 4, 5
Comparison of Blood Tests
The blood tests can be compared as follows: