The serological tests recommended for diagnosing celiac disease are primarily based on the detection of specific antibodies. These include:
Anti-tissue transglutaminase IgA (tTG-IgA)
- This is the preferred single test for the detection of celiac disease in patients over 2 years of age and those with normal serum IgA levels for age
- It is recommended to obtain tTG-IgA in patients with strongly suspected celiac disease and a negative biopsy. A repeat biopsy may be considered if tTG-IgA is positive
- In patients with suspected celiac disease but negative results from serologic tests, it is recommended to obtain tTG-IgA
Total serum IgA
- Total serum IgA is measured to rule out IgA deficiency, which can lead to false-negative results in tTG-IgA testing.
- It is recommended to measure the total IgA level concurrently with serologic testing to determine whether IgA levels are sufficient
IgG-based testing
- In patients with selective total IgA deficiency, it is recommended to obtain IgG-based testing, such as IgG-deamidated gliadin peptides or anti-tissue transglutaminase IgG, at diagnosis and follow-up
- In patients with total IgA levels below the lower limit of detection and IgG against tissue transglutaminase or deamidated gliadin peptide, or endomysial antibody, consider these patients as having celiac disease with selective IgA deficiency rather than seronegative celiac disease
Anti-endomysial IgA (EMA-IgA)
- Although less frequently used due to the labor-intensive nature of the test, EMA-IgA is highly specific and can be used if further confirmation is needed.
HLA determination
- Determination of HLA-based genetic susceptibility to celiac disease has become routine and is useful in defined clinical situations
Ensuring correct diagnosis
- All diagnostic serologic testing should be performed with patients on a gluten-containing diet to avoid false-negative results
- Furthermore, the diagnosis of celiac disease should be confirmed based on clinical data, positive serology, and duodenal histology
In conclusion, the recommended serological tests for diagnosing celiac disease include anti-tissue transglutaminase IgA, total serum IgA, IgG-based testing in cases of IgA deficiency, and anti-endomysial IgA. HLA determination is also a useful tool in certain clinical situations. These tests should be performed while the patient is on a gluten-containing diet to ensure accurate results