From the Guidelines
For patients with IgA deficiency, screening for celiac disease should be done using IgG tissue transglutaminase and IgG or IgA deaminated gliadin peptides, as recommended by the AGA clinical practice guidelines 1. When screening for celiac disease in patients with IgA deficiency, it is essential to use tests that are not reliant on IgA antibodies, as these patients may have false-negative results with standard IgA-based tests.
- The recommended tests include IgG tissue transglutaminase and IgG or IgA deaminated gliadin peptides, which can detect celiac disease in the setting of IgA deficiency 1.
- The AGA clinical practice guidelines strongly recommend testing for celiac disease with these alternative tests in patients with IgA deficiency, citing moderate-quality evidence 1.
- If the results of these tests are positive or if there is a high clinical suspicion despite negative serology, an endoscopic duodenal biopsy remains the gold standard for confirming celiac disease diagnosis.
- It is crucial to inform the laboratory about the patient's IgA deficiency when ordering these tests to ensure appropriate testing is performed.
- The use of IgG-based tests can help identify celiac disease in patients with IgA deficiency, which is essential for initiating a gluten-free diet and preventing long-term complications.
From the Research
Screening for Celiac Disease in Patients with IgA Deficiency
To screen for celiac disease in patients with IgA deficiency, the following approaches can be considered:
- Measurement of IgG-tissue transglutaminase (tTG) antibodies, as IgA deficiency can cause false-negative IgA-based celiac serology results 2
- Use of IgG class counterparts of antibodies against gliadin, endomysium, and tissue-transglutaminase, such as IgG anti-tTG, which have been shown to be valid markers for diagnosing celiac disease in patients with selective IgA deficiency 3
- Simultaneous detection of IgA and IgG antibodies against tissue transglutaminase, which has been shown to have a high diagnostic performance for untreated celiac disease 4
Diagnostic Tests
The following diagnostic tests can be used to screen for celiac disease in patients with IgA deficiency:
- IgG anti-tTG antibody assays, which have been shown to have a diagnostic sensitivity of 75-95% and specificity of 94-100% 3
- IgA/IgG anti-TG2 assays, which have been shown to have a sensitivity of 96% and specificity of 99.5% 4
- IgG anti-deamidated gliadin peptide (DGP) assays, which have been shown to have a lower diagnostic accuracy compared to IgG anti-tTG assays 5
Considerations
When screening for celiac disease in patients with IgA deficiency, the following considerations should be taken into account:
- The presence of IgA deficiency can lead to underdiagnosis of celiac disease if only IgA-based serology tests are used 2
- The use of IgG class counterparts of antibodies against gliadin, endomysium, and tissue-transglutaminase can help improve diagnostic accuracy 3
- The simultaneous detection of IgA and IgG antibodies against tissue transglutaminase can help identify patients with celiac disease who may have been missed by IgA-based serology tests alone 4