--though the test with the highest correlation with small intestinal damage and frank celiac is the transglutaminase IgA assay.

The deamidated anti-gluten IgG test is the most sensitive, but least specific, of the tests in a standard celiac panel. There's been a correlated tendency for that test to be the first to go "positive", though, in cases of celiac and especially in cases of non-celiac gluten sensitivity, the latter being an entity that is still somewhat controversial in some circles.