From the Guidelines
The diagnosis of celiac disease should typically involve a combination of blood tests, including tissue transglutaminase antibodies (tTG-IgA), endomysial antibodies (EMA-IgA), and deamidated gliadin peptide antibodies (DGP-IgA and IgG), as well as total serum IgA levels to rule out IgA deficiency, as recommended by the most recent and highest quality study 1.
Initial Screening
Initial screening for celiac disease is done with serological tests, which are highly sensitive and specific, particularly in adults and children with suspected celiac disease. The most sensitive and specific blood test is tissue transglutaminase antibodies (tTG-IgA) 1.
- Total serum IgA levels should also be measured to rule out IgA deficiency, which could lead to false-negative results.
- Endomysial antibodies (EMA-IgA) and deamidated gliadin peptide antibodies (DGP-IgA and IgG) are also used in the initial screening.
Confirmation of Diagnosis
If blood tests are positive, an upper endoscopy with multiple small intestinal biopsies is usually performed to confirm the diagnosis by showing characteristic intestinal damage such as villous atrophy 1.
- Genetic testing for HLA-DQ2 and HLA-DQ8 haplotypes may be helpful in certain cases, particularly to rule out celiac disease in ambiguous situations, as almost all celiac patients carry at least one of these genetic markers.
- It's essential that patients continue to consume gluten before testing, as eliminating gluten can lead to false-negative results.
Importance of Accurate Diagnosis
The combination of positive serology and characteristic histological findings provides the most definitive diagnosis of celiac disease 1.
- Accurate diagnosis is crucial to prevent delays in diagnosis and to initiate timely treatment with a gluten-free diet, which can significantly improve the quality of life and reduce the risk of complications.
- The diagnosis of celiac disease should be based on the most recent and highest quality evidence, as recommended by the study published in 2022 1.
From the Research
Laboratory Tests for Celiac Disease
The diagnosis of celiac disease involves several laboratory tests, including:
- Serologic tests to measure the levels of certain antibodies in the blood, such as:
- Genetic testing to identify individuals with a high risk of developing celiac disease 3
- Duodenal histology, which is considered the gold standard for diagnosis, but is being replaced by serologic tests in some cases 3, 4
Sensitivity and Specificity of Serologic Tests
The sensitivity and specificity of serologic tests for celiac disease vary, but:
- tTG IgA and EMA IgA tests have high sensitivity and specificity, exceeding 95% in most studies 4
- Antigliadin tests have highly variable sensitivity and specificity, and are generally considered less accurate than tTG and EMA tests 4
- New biomarkers, such as anti-neo-epitope tTg, have been developed and show promise for improving diagnostic accuracy 5
Interpretation of Test Results
The interpretation of test results can be complex, and:
- A positive tTG result with a negative EMA result can be due to the lower sensitivity of the EMA test or the lower specificity of the tTG test 6
- The use of multiple tTG assays can help to increase the accuracy of diagnosis, but the results must be interpreted with caution and in the context of clinical symptoms and other diagnostic criteria 6