Selective IgA Deficiency -IDF Patient/ Family Handbook

Also on IgA deficiency affecting blood and stool testing:

I have heard some doctors say you don't need to worry about IgA deficiency in celiac testing unless you are completely deficient (less than 7)... that you still make enough IgA for it to show up on the tests.

I've heard other doctors, including one of the big specialists (but can't remember who) that below range IgA could affect those results. I would imagine it could go either way.

I think you are right that the stool testing is also based on IgA testing, and can be false negative in IgA deficient people. I'm pretty Dr. Fine addresses the subject somewhere on his website, but I couldn't find it just now. I would think if you are not completely IgA deficient, you'd have a higher chance showing positive on the stool test than the blood test... just because it is a much more sensitive test... but that a false negative would be possible. But, that is just my opinion.