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Tests for IgA Antibodies to Tissue Transglutaminase Vary Too Much For Easy Commutability

Celiac.com 08/26/2015 - People with IgA antibodies to tissue transglutaminase (anti-tTg) likely have a higher risk for celiac disease. Some clinicians and researchers have suggested that common multiples of the upper limit of normal (ULN) be useful tool in improving diagnostic pathways, as well as continuity between tests.

Photo: CC--Alexandre DulaunoyHowever, a new study suggests that both sensitivity and specificity of tests for IgA antibodies to tissue transglutaminase vary widely by individual kit, and that their test values are not easily commutable using common multiples of the ULN to correct for inter-assay variations. Commutability just means the ability to make sure that two different tests really are equal. If results of different tests are commutable, it means that they are equal. In this case, the term applies to test results for various representative samples from healthy and diseased individuals.

For the study, the research team recently looked at the use of immunoassays for the detection of IgA antibodies to tissue transglutaminase, and also sought to better understand of the significance of multiples of the upper limit of normal and inter-assay correlations. The research team included B.B. Suh-Lailam, K.W. Davis, and A.E. Tebo. Using indirect immunofluorescence assay (IFA) as reference, the team assessed characteristics of four anti-tTG IgA assays relative to endomysial IgA (EMA).

They also assessed commutability between anti-tTG immunoassays and/or EMA based on manufacturer's recommended cut-off values and three common multiples of ULN (3×, 5× and 10×). To do this, they analyzed samples from 200 patients and 100 healthy individuals.

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They found that, at manufacturer's cut-off, the sensitivities for the tTG assays ranged from 72.5% to 98.6% and specificities from 60.3% to 99.2%. The percent positive agreements between any anti-tTG and EMA or any two anti-tTG immunoassays varied from 56.7% to 98.0% and 46.7% to 100.0%, respectively.

At 3×, 5× or 10× ULNs, the inter-rater reliability as measured by Cohen κ between any two anti-tTG assays were quite variable and ranged from 0.28 to 0.96, 0.26 to 0.89 or 0.13 to 0.78, respectively.

Furthermore, the percent positive agreements between any two anti-tTg IgA immunoassays ranged from 83.1% to 98.2%, 92.0% to 100%, or 100%, at 3×, 5× or 10×, respectively.

Hence, the team's basic takeaway that result parameters for tTG IgA immunoassays or tTG IgA and EMA vary by kit, and thus common multiples of the ULN are not enough to correct for variation between tests.

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I believe the talk around this forum is that cheerios are not gluten free enough for people with celiac at this time. I don't know if anything has changed on that and when their lawyer calls me I'll quickly delete this. haha

Could be we generally say get off of dairy for a few months when going gluten free. The part of the intestines that produce the enzymes, and help break down dairy are associated with the tips of the villi, which are the most damaged if not gone in celiacs. THIS is why most of us end up with a lactose intolerance early on. And most can introduce it later after healing. As to her symptoms with it there was a bunch of research about dairy permeated the gut and causing neurological issues in a autism study I was looking at years ago. And there have been other studies about damaged intestines and how the hormones in milk can easier effect ones body. Personally I also have a huge grudge against dairy on a personal level as it is not natural to suck on a cows tits and drink the stuff, nor your dogs, nor a rabbits......I mean come on even Human Breast milk you would find odd to drink as an adult right? Back in the past dairy was a great way to get calories and fats when there was famine, etc around I mean it is meant to make a calf grow into a 500+lb cow. But on a genetic and hormonal level it is not really for human consumption and now days the whole corporate BS propaganda push and dairy farms shove that oh its healthy stuff down your throat. There are plenty of dairy free options for everything feel free to message me if you need help finding anything I have been dairy free for over a decade.

The full celiac panel checks TTG IGA and IGG, DGP IGA and IGG, IGA, EMA as Jmg stated above. Your test included TTG IGA and IGA. If your IGA was low, a low on TTG IGA would be inconclusive. But your IGA is fine. A high on any one test is a positive for celiac and should lead to an endoscopy for confirmation. So I'd get tested for TTG IGG, DGP IGA and IGG and EMA since there are symptoms. Warning I'm not a doc.

I did a gluten challenge for my endoscopy and requested a second blood test after my follow up with the consultant. I never did see those results but my GP said no celiac was indicated: Which left me gluten free for life, that wasn't an option after the challenge, but with a less satisfactory diagnosis, one by omission rather than the definitive 'you're celiac' one I was expecting. Yes! I have been 'properly' glutened on a couple of occasions but on several more I've detected a change or a reaction based on what could only have been trace amounts. NCGS is as yet poorly understood but patients tend to have more neuro symptoms than digestive. That's definitely been my experience, although it was only after going gluten free that I realised quite how many digestive symptoms I had just been living with as 'normal'. Close friends and family get the full explanation. 'I have an auto immune disease similar to 'coeliac etc.' If they stay awake long enough I'll tell them about the less than perfect testing process I went through or the Columbia Med research and the possibility of a blood test soon. They can see the difference between me on gluten and off it so they understand its not all in my head* If I'm ordering food in a restauarant or asking questions about food prep etc I will often just self declare as coeliac - people are aware of that and understand those requests are medical rather than fad diet based. I don't have any problem doing this, I'm not going to claim that and then cheat on dessert for instance and to be honest I expect once the research is complete the two conditions may wind up alongside others as different faces of the same coin. In the meantime I safeguard my health and avoid getting into a detailed conversation about genuine gluten sensitivity versus faux hipster posturing! *apart from the bits which are in my head

I originally had it on my face and scalp. (22 years ago) First biopsy with dermatologist came back as folliculitis. Then when I had a new outbreak on my upper back, she was able to remove a nice clean blister and we got the diagnosis of DH. She started me on Dapsone (100mg/day) and gluten free diet. Now I take 25-50 mg/day. My understanding at the time was that DH was the skin version of Celiac. Did a lot of research on my own. I met Dr. Peter Green at a Gluten free Vendors Fair and he said that a diagnosis of DH IS a diagnosis of Celiac, even if no other symptoms. So I stay gluten-free