From the Guidelines
The IgG gliadin and transglutaminase test is primarily used to diagnose celiac disease, particularly in patients with selective IgA deficiency, as it detects IgG antibodies to gliadin and tissue transglutaminase. This blood test measures antibodies that the body produces in response to gluten proteins and tissue transglutaminase, an enzyme that becomes a target of the immune system in celiac disease. The test is most accurate when performed while the patient is still consuming gluten, as antibody levels decrease after starting a gluten-free diet. Some key points to consider when interpreting the results of this test include:
- The test is not the first-line screening test for celiac disease, as tissue transglutaminase antibodies (tTG-IgA) and deamidated gliadin peptide antibodies (DGP-IgA and DGP-IgG) are now considered more sensitive and specific 1.
- A positive blood test typically requires confirmation with an intestinal biopsy for a definitive diagnosis of celiac disease 1.
- The test may also be used to monitor compliance with a gluten-free diet in diagnosed celiac patients.
- In cases of selective IgA deficiency, IgG tissue transglutaminase or deamidated gliadin peptide should be considered 1. It's essential to note that while IgG anti-gliadin antibodies were once commonly used for celiac testing, newer tests are now preferred due to their higher sensitivity and specificity 1. The diagnosis of celiac disease should be based on a combination of serologic testing, intestinal biopsy, and clinical evaluation, as outlined in recent guidelines 1.
From the Research
IgG Gliadin and Transglutaminase Test
The IgG gliadin and transglutaminase test is used to diagnose and monitor celiac disease, an autoimmune disorder that causes the immune system to react to gluten.
- The test measures the levels of IgG antibodies against gliadin and transglutaminase in the blood 2, 3, 4, 5, 6.
- Gliadin is a protein found in wheat, barley, and rye, while transglutaminase is an enzyme that helps to break down gliadin in the small intestine.
- The presence of IgG antibodies against these proteins indicates that the immune system is reacting to gluten, which can cause damage to the small intestine and lead to symptoms such as diarrhea, abdominal pain, and fatigue.
Purpose of the Test
The IgG gliadin and transglutaminase test is used for several purposes:
- To diagnose celiac disease in individuals who are suspected of having the condition 3, 4, 6.
- To monitor the effectiveness of a gluten-free diet in individuals with celiac disease 2, 5.
- To detect the presence of IgG antibodies against gliadin and transglutaminase in individuals with IgA deficiency, who may not produce IgA antibodies against these proteins 6.
Sensitivity and Specificity
The sensitivity and specificity of the IgG gliadin and transglutaminase test vary depending on the study and the population being tested:
- One study found that the test had a sensitivity of 92% and a specificity of 98% for diagnosing celiac disease 3.
- Another study found that the test had a sensitivity of 100% and a specificity of 61% for detecting celiac disease in individuals who had not commenced a gluten-free diet 4.
- A more recent study found that the test had a sensitivity of 97% and a specificity of 100% for diagnosing celiac disease, and that the combination of IgA and IgG antibodies against transglutaminase was able to detect antibodies in all patient samples 6.