The Question: “How long you would recommend doing a gluten-challenge for before I get my blood test done?”
“I have been gluten-free for over a year, but now I’m into my second week of the gluten-challenge (my GP said it needs 3 weeks, at 2 slices of bread a day) before testing for the gene and for anti-TTG antibodies. I’d rather stop having so much gluten as soon as possible, but without risking an unreliable diagnosis. Thanks”
The Context: Eating gluten to deliberately make you sick! A gluten challenge is usually embarked upon to make a definitive diagnosis of celiac disease. But such a challenge is inherently flawed. To make any sense of the “challenge”, you first need to define the end-points of the challenge, and then know what action to take when you get the results.
Complexities of a gluten-challenge
To sort out the difference between celiac disease and gluten-sensitivity is hard, because there is no clear distinguishing line between them. The symptoms are the same. The fundamental difference in is the definition: celiac disease is defined as gut damage caused by gluten. These conditions can also also co-exist. Gut damage can be slow to develop, such that in early celiac disease, the gut damage may not yet have developed. This can take decades.
1) The end-points of the gluten-challenge differ. To diagnose celiac disease, you are looking for gut damage provoked by gluten. To diagnose gluten-sensitivity, you are looking for symptoms provoked by gluten.
2) The development of CD (gut damage) is very unlikely in people without the HLA gene markers (DQ2 and/or DQ8). So this should be tested for prior to a gluten-challenge. If absent, a prolonged gluten challenge will never cause gut damage.
3 Gut damage is traditionally confirmed by small bowel biopsy. But this cannot be viewed as the “gold standard”, because there are many pitfalls to the accuracy of this test. Early damage might not be seen through a microscope. It can take months or even years on gluten for observable gut damage to be seen. http://drrodneyford.com/extra/documents/236-no-gold-standard.html
4) Blood tests (DGP, tTG and EMA) are accurate at detecting gut damage, but can take months and years to become positive.
5) High doses of gluten are needed to damage the gut. A review (http://www.ncbi.nlm.nih.gov/pubmed/24284613) suggested that a 3-month high-dose gluten-challenge is suitable to diagnose the majority of CD patients. But in some cases, prolonged challenge was needed to verify diagnosis. These studies were mostly done on patients who had already been demonstrated previously to have celiac disease. In children, between 70-100% developed positive celiac blood test results within three months while eating gluten. In adults, between 50-100% showed positive test results within three months. But in previously undiagnosed people, it might take a lot longer to see a result.
6) If your biopsy is negative after the gluten-challenge, and if you carry a celiac gene, and if you continue to eat gluten, then you need yearly blood tests to determine if you are developing celiac disease (many people with celiac disease have few if any symptoms).
7) If you got symptoms on the gluten-challenge, then this tells you that gluten is bad for you, but symptoms cannot distinguish between celiac disease and gluten-sensitivity. If you get symptoms, you should be on a gluten-zero diet, whatever your diagnosis.
By Rodney Ford