What is the Difference Between tTG IgA and tTG IgG?

The tTG IgA and tTG IgG tests are both serological tests used to diagnose celiac disease based on the detection of anti-transglutaminase antibodies in the blood. The main differences between the two tests are:

1. Target Antibodies: tTG IgA test diagnoses celiac disease based on the finding of transglutaminase IgA antibodies, while the tTG IgG test diagnoses celiac disease based on the finding of transglutaminase IgG antibodies.
2. Preferred Test: The tTG IgA test is the preferred test for most patients, as it is more sensitive and specific in diagnosing celiac disease.
3. IgA Deficiency: The tTG IgG test is used primarily in patients with IgA deficiency, as they may not produce sufficient IgA antibodies. In such cases, the tTG IgG test can help diagnose celiac disease.
4. Cascade Testing: Some laboratories follow a testing algorithm that starts with total IgA measurement. If the level is normal, tTG-IgA is measured. If the total IgA is low, then both tTG-IgA and tTG-IgG are measured. If the total IgA is deficient, only the tTG-IgG and often the DGP-IgG are measured.

Both tests are enzyme-linked immunosorbent assays (ELISA), and their results should be confirmed by a small intestinal biopsy to establish a diagnosis of celiac disease.

Comparative Table: tTG IgA vs tTG IgG

Here is a table comparing the differences between tTG IgA and tTG IgG:

Both tests are enzyme-linked immunosorbent assays (ELISA) and require the presence of a specific enzyme called tissue transglutaminase for their performance. After performing both tests, patients should undergo a biopsy to confirm a diagnosis.