Test results inconclusive?

[416510]

My son has not been keeping up with his growth and his doctor ran a transglutiminase antibody iga test. She called and said the test is inconclusive and she will let me know more when she hears back from a specialist. His value is 92.5 and normal is up to 20 but because it’s not 10x the normal (200) she’s not sure. My understanding after googling is that it warrants confirmation with a biopsy. But it seems very likely right? Or what else could it be?

[trents]

Welcome to the forum, 416510!

How old is your son? Young children will often test negative for the tTG-IGA even when they do have celiac disease because their immune systems are immature. With young children, there should be several different antibody tests run, what we call a "full celiac panel". So, if you son tested positive on the tTG-IGA I would consider that strong evidence that he in fact does have celiac disease.

If your son's tTG-IGA is 70 points higher than the high end of normal range I would consider that unequivocally high. In the UK and perhaps other countries, doctors will commonly assign a diagnosis of celiac disease if the score is 10x normal and forgo the endoscopy/biopsy. If lower than 10x normal, they will want to do an endoscopy/biopsy to confirm. In the USA, it is normal to pursue an endoscopy/biopsy for confirmation, regardless of the antibody score or scores.

[416510]

4 hours ago, trents said:

How old is your son?

Thanks so much for this detailed reply! He’s 3.5. 

[Scott Adams]

The blood test result you mentioned looks like a very high positive result for celiac disease to me, and the next step is normally an endoscopy, but given his age I would also not be very keen to have this procedure done, especially if he has symptoms that go away on a gluten-free diet. 

[416510]

Our doctor asked us to wait 3 weeks and retest. The new tTG-iga is now only 2x the upper limit of normal. Previously it was 4.5x the upper limit of normal. This time they also ran an endomysial antibody test and it was negative. My internet research says this combo is unlikely to be celiac disease (about 15%). But I can’t figure out what might cause the tTG-iga elevation if not celiac disease? We will be doing an endoscopy in about 6 weeks.

[trents]

24 minutes ago, 416510 said:

Our doctor asked us to wait 3 weeks and retest. The new tTG-iga is now only 2x the upper limit of normal. Previously it was 4.5x the upper limit of normal. This time they also ran an endomysial antibody test and it was negative. My internet research says this combo is unlikely to be celiac disease (about 15%). But I can’t figure out what might cause the tTG-iga elevation if not celiac disease? We will be doing an endoscopy in about 6 weeks.

Don't cut back on gluten until after the endoscopy/biopsy. The dairy protein "casein" can damage the villi of the small bowel like gluten does in some people with celiac disease.

[Scott Adams]

3 hours ago, 416510 said:

Our doctor asked us to wait 3 weeks and retest. The new tTG-iga is now only 2x the upper limit of normal. Previously it was 4.5x the upper limit of normal. This time they also ran an endomysial antibody test and it was negative. My internet research says this combo is unlikely to be celiac disease (about 15%). But I can’t figure out what might cause the tTG-iga elevation if not celiac disease? We will be doing an endoscopy in about 6 weeks.

I am not sure where you get a 15% chance of celiac disease with a 2x normal positive tTG-iga test result, but I seriously doubt this conclusion. The article below has recently been updated with the latest info on probabilities and accuracy of each test.

As for the EMA-IgA (endomysial antibodies IgA): "The sensitivity of this test is approximately 50-90%. This means that the test may produce a false negative result in some people with celiac disease who do not have elevated levels of IgG antibodies to tissue transglutaminase, and the specificity (its ability to correctly identify people without celiac disease) is approximately 70-90%." Children are more likely than adults to have false negative results on some celiac disease blood tests.

As for the tTG-IgA (tissue transglutaminase IgA) 2x positive results, the test is estimated to have a sensitivity of approximately 90%, which means that it correctly identifies 90% of people with celiac disease. It also has a high specificity of around 95%, which means that it correctly identifies 95% of people who do not have celiac disease.

 

[416510]

Thanks for your response and link. We’re keeping our mind open and of course looking forward to hopefully getting it resolved soon. 
Fyi here is where I pulled (approximately) 15% chance (with the specific combo of elevated tTG iga and negative endomysial antibody - sorry if that was confusing) from:

https://pubmed.ncbi.nlm.nih.gov/33166550/

https://gutsandgrowth.com/2015/04/07/how-likely-is-celiac-disease-if-my-ttg-test-is-only-a-little-bit-abnormal/

[Scott Adams]

Yes, I understood and thank you for the links. The EMA-IgA (endomysial antibodies IgA) has a high false negative rate, so that is why I posted that info. The tTG-IgA (tissue transglutaminase IgA) does not have a false high false positive rate, and since there have been two positive tTG-IgA (tissue transglutaminase IgA) tests that were both very high, to me anyway, it seems very unlikely that there would be a low chance of celiac disease.

[knitty kitty]

@416510,

You may want to ask for the anti-DGP - IGg tests.  It's part of the"complete Celiac panel" @trents mentioned.  

Here's some studies about it...

Diagnostic accuracy of anti-DGP (IgG) for celiac disease

https://pubmed.ncbi.nlm.nih.gov/37025242/

And...

Diagnostic Value of Immunoglobulin G Anti-Deamidated Gliadin Peptide Antibody for Diagnosis of Pediatric Celiac Disease: A Study from Shiraz, Iran

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9284110/