Gentetic Testing

[Dora Ann]

Thank you for allowing me to post and good morning. I am requesting information on genetic testing and the accuracy. I was diagnosed celiac based off my labs; I will provide a timeline of my test. 

Thank you. 

2/11/2021: Tissue Transglutaminase AB, IgG 19H u/ml. 

2/14/2021: Immediately went gluten-free saw amazing results. 

3/07/2021: HLA-GQ2, HLA-DQ8 - negative (this I am unsure of as my son has 80% of my symptoms, went gluten-free (without seeing the doctor, because he 20 yr. old stubborn boy) and saw complete relief. 

3/25/2021: Upper GI w/ ballon and biopsy - No evidence for Celiac. (I have been gluten-free since 2/14/2021 - was unaware at the time I had to be on a Gluten diet or testing would be altered, the doctor didn't tell me 😞 . 

However, my question is about HLA-GQ2, HLA-DQ8 testing. Since I am positive Tissue Transglutaminase AB, IgG but negative HLA-GQ2, HLA-DQ8 - what are your thoughts? If NOT celiac when what could positive Tissue Transglutaminase AB, IgG be? I have obviously seen wonderful results GI wise to stay on diet, but my concerns are if genetic testing is negative then how can that be so with my son responding to gluten-free diet as well. 

Any thoughts or ideas would be wonderful. 

Thank you

 

 

[trents]

Welcome to the forum, @Dora Ann! Your post is a little confusing as it's not clear to me whether you are seeking clarification for your own antibody and genetic testing results or your 20 year old son.

So, let me take a stab at this, assuming you are asking for yourself. First, I understand you to say the tTG-IGG antibody test was positive for yourself. Were there any other antibody tests run and were any of them positive? The most important antibody test is not the tTG-IGG but the tTG-IGA. The tTG-IGA is a more reliable marker for celiac disease than the tTG-IGG which is a secondary test. However, the tTG-IGG can be very helpful in cases where the testing was done after the gluten free diet was started and it can point to celiac disease. Was any of the antibody testing done while you were still consuming normal amounts of gluten?

Second, the HLADQ2 and HLADQ8 genes are not the only genes that have been connected with celiac disease but at this point in time they are considered to be the primary ones. Not having DQ2 and/or DQ8 does not mean you cannot have celiac disease.

Third, you and your son could have NCGS (Non Celiac Gluten Sensitivity) instead of celiac disease. It shares many of the same symptoms with celiac disease and is 10x more common. However, there is no test for NCGS. The antidote is the same, however and that is total avoidance of gluten for life. There is likely a genetic component to NCGS as well and that may be why both you and your son are responding well to removing gluten from your diet.

Edited January 17, 2024 by trents

[Dora Ann]

Thank you for your response @trents. Sorry I was confusing, it's a brain-fog kind of day lol. 

I listed the testing above that I had for me, but I am going to dig through my records and see if I see any more labs. The TtG was done while consuming gluten, all others where after a gluten free diet. However, I will look in my records to see if they did anymore ...

I FOUND MORE LABS!! Didn't even know they ran these. Never told me !!! Uggg  

09/21/2023 Deamidated Gliadin Abs, Iga - negative (gluten-free diet)

09/21/2023 t-Transglutaminase (tTg) IgA -  negative (gluten-free diet)

09/21/2023 Immunoglobulin A, Qn, Serum - negative (gluten-free diet) 

Thank you so much for your help. 

[Dora Ann]

Would any of those 3 tests (9/21/23) been affected on a gluten-free diet? 

[RMJ]

14 minutes ago, Dora Ann said:

Would any of those 3 tests (9/21/23) been affected on a gluten-free diet? 

Yes, the first two would be affected by a gluten free diet (deamidated gliadin and t-Transglutaminase).  

“Negative” is a strange result for total IgA (Immunoglobulin A, Qn, serum).  Was there a number and a range?  This looks like total IgA which is tested to be sure the other IgA tests are valid.

[Dora Ann]

09/21/2023 Deamidated Gliadin Abs, Iga - 4 units (0-19)

09/21/2023 t-Transglutaminase (tTg) IgA -  <2 U/mL (0-3)

09/21/2023 Immunoglobulin A, Qn, Serum -  123 mg/dL (87-352)

I was just summarizing results instead of typing it all out ❤️ 

 

[trents]

All testing for celiac disease is compromised when the gluten free diet is already in place. The blood antibody tests are measuring the antibody levels in response to the ingestion of gluten. For those with celiac disease, gluten is interpreted as an invader when it comes in contact with the villous lining of the small bowel. The immune response produces inflammation and antibodies. The inflammation damages the villous lining over time which in turn reduces the ability of the small bowel to absorb the nutrients in the food we eat. When gluten consumption is discontinued, the antibody levels begin to drop, thus compromising the blood tests that are designed to detect them. Over and over, we have forum participants who report that their physicians failed to explain to them that they should not begin the gluten free lifestyle until all testing is complete. It is appalling. Of course, the genetic testing is not affected by going gluten free.

[Scott Adams]

Agreed, you need to be eating gluten before any tests for celiac disease, with the exception of genetic tests.

Here is more info about how to do a gluten challenge for a celiac disease blood panel, or for an endoscopy:

Quote

"...in order to properly diagnose celiac disease based on serology and duodenal histology, doctors need patients to be on gluten-containing diets, even if they are causing symptoms, and this is called a "gluten challenge."

• Eat gluten prior to celiac disease blood tests: The amount and length of time can vary, but is somewhere between 2 slices of wheat bread daily for 6-8 weeks and 1/2 slice of wheat bread or 1 wheat cracker for 12 weeks 12 weeks;
• Eat gluten prior to the endoscopic biopsy procedure: 2 slices of wheat bread daily for at least 2 weeks;

and this recent study recommends 4-6 slices of wheat bread per day:

 

 

[RMJ]

The 9/21/23 tests include two celiac antibody tests which would be affected by a gluten free diet, and a total IgA test which is in the normal range (good!). (If the total IgA had been too low then different celiac tests might have been necessary).

[Judi Magner]

Do you have to be fasting to do the HLA-DQ2 and HLA DQ* blood test? I did these and they were both positive but I was not fasting.  My ND said to consider myself Celiac. 

[Scott Adams]

No, for genetic tests it does not matter whether you are eating gluten or not, it won't affect the results.

[trents]

No, the genetic testing is not affected by going off gluten because you're talking about something you are born with. We were referring to antibody testing to biopsies when we said all testing is affected by going gluten free.