Anti-deamidated Gliadin vs. Anti-deamidated Gliadin IgA and IgG
No, anti-deamidated gliadin is not the same as anti-deamidated gliadin IgA and IgG specifically; rather, it refers to antibodies against deamidated gliadin peptides that can be of either IgA or IgG isotype, which are tested separately in clinical practice.
Understanding Deamidated Gliadin Antibodies
- Deamidated gliadin peptide (DGP) antibodies are serological markers used in celiac disease diagnosis that can be measured as either IgA or IgG isotypes 1
- These antibodies recognize gliadin peptides that have been modified (deamidated) by the enzyme tissue transglutaminase (tTG), which is the major autoantigen in celiac disease 1
- When laboratories test for "anti-deamidated gliadin," they are typically measuring either IgA antibodies, IgG antibodies, or both isotypes separately 1
Clinical Testing Approaches
In clinical practice, anti-deamidated gliadin antibodies are tested as specific immunoglobulin isotypes:
- Anti-DGP IgA: Measures immunoglobulin A antibodies against deamidated gliadin peptides 1
- Anti-DGP IgG: Measures immunoglobulin G antibodies against deamidated gliadin peptides 1
- Anti-DGP IgA+G: Some assays use a conjugate reactive to both isotypes, giving a positive result if either isotype is present 2
The sensitivity and specificity differ between these tests:
Clinical Utility and Comparison with Other Celiac Tests
- Anti-DGP antibodies have reasonably high accuracy for celiac disease diagnosis, although generally considered inferior to tissue transglutaminase (tTG) IgA testing 1
- Anti-DGP IgG is particularly valuable in IgA-deficient patients, where it shows comparable diagnostic sensitivity to IgG-anti-tTG (88.2% vs. 91.2%) 3
- The American Gastroenterological Association recommends IgG deamidated gliadin peptides as an option for testing in IgA-deficient patients 1
Important Clinical Considerations
- Anti-DGP testing should be performed while patients are on a gluten-containing diet to avoid false negative results 1
- In children under 2 years of age, combining tTG-IgA with IgG and IgA deamidated gliadin peptides is recommended for improved sensitivity 1, 4
- Studies show good correlation between tTG-IgA and DGP-IgG (r = 0.69), and between tTG-IgA and DGP-IgA (r = 0.67) 5
Clinical Applications
- Anti-DGP IgG is the preferred test in IgA-deficient patients suspected of having celiac disease 1, 3
- In standard celiac disease testing, IgA tissue transglutaminase (tTG-IgA) remains the primary recommended screening test 1, 4
- Some laboratories offer combined detection of IgA/IgG anti-DGP, which may improve sensitivity but can slightly reduce specificity 6
In summary, when referring to "anti-deamidated gliadin," it's important to specify the immunoglobulin isotype (IgA or IgG) as they have different diagnostic characteristics and clinical applications in celiac disease testing.