Interpreting Blood Results - Low iGA

[Kenziee]

Hello! 
Looking for some advice regarding a recent blood test for coeliac disease. I’ve been experiencing coeliac symptoms for years but have only recently requested a test to check for the autoimmune disease because my symptoms have progressively gotten more severe this past year. I received my results and was told it was negative but I’m worried it may be a possible false negative. I have low iGA, which I think may be interfering with the accuracy/reliability of the testing. 

My iGA was 0.47g/L so it’s most definitely low. I think I may have an iGA deficiency - though I’m not sure. Do you think this may be interfering with the coeliac testing? Should I ask for a different test instead that doesn’t rely upon my (lack of) iGA antibodies? 
 

Advice would be extremely appreciated, thank you! 

[Scott Adams]

You are correct and low IgA can cause false negatives on IgA-based antibody tests for celiac disease. If you have your tTg-IgA results, feel free to share them (please include the reference ranges).

This article might be helpful. It breaks down each type of test, and what a positive results means in terms of the probability that you might have celiac disease. One test that always needs to be done is the IgA Levels/Deficiency Test (often called "Total IGA") because some people are naturally IGA deficient, and if this is the case, then certain blood tests for celiac disease might be false-negative, and other types of tests need to be done to make an accurate diagnosis. The article includes the "Mayo Clinic Protocol," which is the best overall protocol for results to be ~98% accurate.

 

 

[Kenziee]

Thank you for your response! I’ll put my details from the ttg iga test and my general iga count below: 

tTg-IgA level - 0.6 U/ml (reference ranges: 0.00-3.90U/ml = negative, 3.90-10.0U/ml = weak positive, >10.0U/ml = positive) 

IgA level - 0.47g/L (reference ranges for IgA: 0.80-2.80g/L = regular IgA, <0.8g/L = low IgA) 

Thank you. 

[trents]

By some chance had you already begun to limit gluten consumption before the blood draw was done?

As Scott, mentioned, the tTG-IGA test is the most popular celiac antibody test ordered by physicians to check for celiac disease. It is quite sensitive and quite specific but low total IGA and, anemia, diabetes and low gluten consumption can skew it toward a false negative. And as Scott also mentioned, there are other blood tests that can be run in these cases that can catch celiac disease even thought they might not be as well-rounded as the tTG-IGA. If your healthcare system will allow, request these to be run: DGP-IgA and DGP-IgG (Deamidated Gliadin Peptide). It is also possible that you have NCGS (Non Celiac Gluten Sensitivity) which shares many of the same symptoms with celiac disease, is 10x more common but for which there is not yet a reliable test. Same antidote as celiac disease, however, and that is a gluten free diet.