TTG IgA - Normal / EMA IgA - Positive - Could anything else cause this result?

[nayr]

As the title says, I've been pretty unwell the last few months with my symptoms getting much worse the last few weeks and my GP ordered a blood test which included a TTG IgA and EMA IgA test.

The TTG IgA came back in the normal range - Result 5 u/mL (Range 0.00 - 6.90 u/mL) but my EMA IgA came back as positive.

I have a biopsy soon but I'm slightly confused by this result, from a number of results I've seem of newly-diagnosed Celiac's, they seem to have an elevated TTG IgA level which I appear to not have.

It might be worth noting that these are the only markers that have been tested thus far.

 

My question being, could the positive EMA IgA be a false positive (is this likely?) or could this positive be related to something else (Even though EMA IgA is pretty specific).

Thanks!

[trents]

Welcome to the forum, nayr!

The EMA is the most specific of all the antibody tests for celiac disease but is less sensitive than the tTG-IGA. So, when tTG-IgA is negative and EMA is positive, that reinforces a celiac disease diagnosis. It is not abnormal at all to have some celiac antibody tests to be negative while others are positive. This is more common than not. If a total serum IGA was not performed, and you don't mention it so we assume it was not, it is possible that a low score for that one was driving down the tTG-IGA into the negative range. There is always the possibility that the positive EMA was caused by something else but the likelihood of that is very slim. What are your symptoms? Have you had a CBC and a CMP done lately to look for other evidence of celiac disease such as low iron or elevated liver enzymes?

As you may know, there are a number of antibody tests that can be run for celiac disease in addition to the tTG-IGA and the EMA but they are less specific. These would be included in a "full celiac panel" which seems not to have been done in your case. Nonetheless, they can provide supporting evidence when diagnosing celiac disease. 

But I should mention that you must not begin the gluten free diet or reduce your gluten intake until the biopsy is complete.  

Edited September 8, 2023 by trents

[Scott Adams]

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.

Quote

The sensitivity of a test refers to its ability to correctly identify individuals with the condition. For the EMA-IgA blood test, the sensitivity is generally very high, ranging from 90% to 98%. This means that the test can accurately detect celiac disease in a significant percentage of people who have the condition.

The specificity of a test refers to its ability to correctly identify individuals without the condition. For the EMA-IgA blood test, the specificity is also high, typically around 95% to 100%. This indicates that the test can effectively rule out celiac disease in individuals who do not have the condition.