False tTG3 Test?

[SB04]

Hi all,

about a year ago I had some blood tests done through a naturopath because I had constant hives and no idea why. They would go away for a few days with an antihistamine medicine but always come right back.

Anyways, she did an igg test (which i now know is terribly unreliable) and it was pointing to gluten sensitivity. there was another test too, that tested for wheat iggs, igas and several other things, among which were Transglutaminases. The only one that came up as high for me was the tTG3 igg result, which shows an autoimmune response in the skin, commonly dermatitis herpetiformis in celiac patients. I was told it was gluten causing it but not celiac.

Fast forward to now, I still have hives, I've been gluten free (although I have no reation to gluten when I accidentally have it), and I've been doing research to try and figure out what is wrong. I've heard that those initial igg tests are unreliable, and that maybe gluten isn't the issue, but from what I've read it sounds like the Transglutaminase tests are very reliable? I'm wondering if I somehow got a false positive, because I definitely don't have dermatitis herpetiformis or any typical celiac rashes. Has anyone had a similar experience?

[trents]

Welcome to the forum, @SB04!

Let's cut to the chase. Did they run a tTG-IGA and a total IGA? Total IGA goes by many names but it checks for IGA deficiency. If you are IGA deficient, IGA test scores will be artificially low and it can result in false negatives. The tTG-IGA is the centerpiece of celiac disease antibody testing. 

Dermatitis herpetiformis is the epidermal expression of celiac disease. Most who have dermatitis herpetiformis also have damage happening to the small bowel lining as well but a small percentage do not. But dermatitis herpetiformis has a characteristic appearance to it, with the rash bumps having pustules in the center. It is also accompanied by a very uncomfortable itch. From what you describe, your rash doesn't sound like dermatitis herpetiformis.

The IGG antibody tests are not quite as specific for celiac disease as are the IGA tests but they aren't terrible either. This may be helpful: 

 

Edited June 4, 2025 by trents

[SB04]

Thanks!

I don't think it was a total IGA test, it was called "Array 3X - Wheat/Gluten Proteome Reactivity & Autoimmunity" and it tested a bunch of wheat proteins and transglutaminase for both IgG and IGAs.  

[Russ H]

The problem with a a multiple screening test like this is that it is likely to generate at least one result that is outside the normal range in a healthy person leading to futile investigations. The pathogenesis of dermatitis herpetiformis makes it unlikely that someone would have raised IgA-tTG3 but not raised IgA-tTG2. Suspected dermatitis herpetiformis should be referred to a specialist for diagnosis. dermatitis herpetiformis causes a specific rash and symptoms - not merely hives.

https://bestpractice.bmj.com/topics/en-gb/3000326

[knitty kitty]

@SB04,

Have you been checked for B12 deficiency? 

A deficiency in Vitamin B12 will cause hives and also raise the tTg 3 IgG level, even in people without Celiac Disease.  

You can have B12 deficiency without having Celiac Disease.  

All eight B vitamins work together.  Do not supplement just a single B vitamin.  

Best wishes.