Is genetic testing enough for a diagnosis?

[driley247]

Hello to all! I am 50 years old and began getting ill in the summer of 2020. While struggling with horrible joint/bone/muscle pain, constipation, coordination issues, extreme exhaustion and a host of scary neurological symptoms, I was sent for an MRI, neuropsychological tests, and upper endoscopy and colonoscopy. All of those came back negative. However- and herein lies my question- at my wife’s suggestion I tried eating gluten-free (and taking B12 and D) for a month with some improvement. Because of this, my doctor didn’t want me to take the gluten challenge and had the genetic testing done. When it came back positive for FDQ8 (DQA1 03XX, DQB1 0302), she told me it was Celiac disease. QUESTION: Is this test result, taken together with my symptoms and improvement on gluten-free diet enough for a diagnosis? My concern is that I don’t want to assume I have celiac disease if it isn’t adequate data. Recently, I was out of work for 4 days with many of the same symptoms. I do understand Celiac damage takes a long time to recover from, and perhaps I was glutened. Just trying to cover my bases. Thoughts and suggestions welcome!

[trents]

Genetic testing cannot establish that you have celiac disease. It can only establish that you have the potential for celiac disease, which you do, having the FDQ8 gene. There is one other gene that has been associated with celiac disease so far and there may be others. Many or most people that have the genetic potential for celiac disease don't actually develop the disease. It takes both the genetic potential and some kind of a triggering stress event such as a viral infection for the gene or genes to be expressed.

Having said that, you do have some symptoms that could definitely point to celiac disease. But your symptoms could also point to NCGS (non celiac gluten sensitivity). The only way to establish that you have celiac disease or to distinguish it from NCGS is to have actual testing done for celiac disease. The first stage of diagnostic testing is a serum antibody test. Celiac disease causes damage to the villi of the small bowel from inflammation. The inflammation produces antibodies. If you test positive for celiac antibodies then you very likely have celiac disease. But you would need to be eating gluten regularly (the equivalent of two slices of wheat bread daily) for 6-8 weeks before the test in order for it to be valid. The second stage of testing is an endoscopy with biopsy of the small bowel villi and is considered to be the gold standard for celiac disease testing. The pretest gluten challenge for that is only 2 weeks of regular consumption of gluten. Both Celiac Disease and NCGS produce many of the same symptoms and the antidote is the same for both, namely total abstinence from gluten for life. NCGS does not damage the small bowel villi and so if you have gluten caused symptoms but no damage to the villi then a diagnosis of NCGS is made. Could you tuff it out and go back on gluten until some actual testing is done?

[Scott Adams]

I agree with @trents and your doctor seems to be missing some key information. At this point you might be able to say that you have non-celiac gluten sensitivity, but not celiac disease. Around 10x more people have NCGS than celiac disease, and unfortunately there isn't a test for it, yet the treatment is the same, a gluten-free diet for life. Perhaps your doctor knows this, and realized that you may need a gluten-free diet either way.