Celiac disease is hugely undiagnosed. I meet with at least one person per week who has multiple signs and symptoms of celiac disease who is searching for an answer. The answer may be gluten-free diet, but how do you know definitively if you have celiac disease? Here are the tests available to help to diagnose or rule out celiac disease.
There are multiple blood tests that should be done to screen for celiac disease. I say “screen” for celiac because blood tests cannot diagnose someone with celiac disease. If one of these tests is positive for celiac, further testing will be recommended to diagnose celiac. You must be eating gluten on a regular basis for these tests to be valid. From Celiac Central and the University of Chicago Celiac Disease Center, these are the tests to be ordered:
- Total IgA
- Anti-tissue transglutaminase (tTg)
- Anti-endomysium (EMA)
- Anti-deamidated gliadin peptides (IgG and IgA-DGP)
- IgG-AGA, is not as good for diagnosing celiac but is the only biomarker that has been associated with non-celiac sensitivity
Physicians don’t recognize when a person presents with celiac disease; that is the first problem contributing to celiac disease being under-diagnosed. The next problem is that most physicians only order tTg. This test has a high tendency towards falsely negative results, which means that the test comes back negative and you are told that you don’t have celiac, but you actually do have celiac. That is what happened with me. My physician ran the test 4 or 5 times over the 8 years that we were searching for the cause of my osteopenia, gut distress and elevated liver enzymes. My tTg level was always normal. My doctor also ran tests looking for nutrient deficiencies and those came back normal too, even though I had physical signs of a few nutrient deficiencies. Finally, I asked for an intestinal biopsy.
If one of the tests above comes back positive an intestinal biopsy will be recommended to confirm celiac disease. If the above tests all come back negative, but you still suspect celiac disease, you may consider genetic markers, a trial gluten-free diet or an intestinal biopsy.
You must be eating gluten on a regular basis to have an intestinal biopsy. An intestinal biopsy is used to diagnose celiac disease. Celiac is an autoimmune condition that results in flattening of villi in the small intestine. Villi are tiny, finger-like projections that cover the surface of your gastrointestinal tract and absorb nutrients from food. An intestinal biopsy is done to assess whether or not villi have been damaged.
Intestinal biopsy is considered the “gold-standard” for diagnosis of celiac. However, there is still a risk of false negative results with intestinal biopsy, particularly in people 18 years and younger or when the biopsy is done incorrectly. The risk of false negative is dramatically reduced when the gastroenterologist does the biopsy correctly by taking 4-6 or more biopsy samples from throughout the small intestine, including the duodenal bulb, and when a special stain is used to identify intraepithelial (between cell) inflammation.
One of the most frustrating cases I had last year was a young woman who had an intestinal biopsy done incorrectly. Only one sample was taken and she was told that she did not have celiac disease. She continued to eat gluten until her health had spiraled so out of control that she started a gluten-free diet on her own and immediately felt better. She had all the signs and symptoms of celiac and a cousin with celiac. In her case, her positive response to a gluten-free diet, signs and symptoms of celiac and family history (i.e. genetics) provided the diagnosis of celiac disease. Our work together centered primarily on working towards acceptance of her diagnosis and living well on a gluten-free diet.
Approximately 95% of people with celiac disease have one of these two genes, HLA-DQ2 or HLA-DQ8. Having one of these genes does not mean that you have celiac, and so genetic testing cannot diagnose you with celiac. However, if you do not have one of these genes, it is highly unlikely that you would ever develop celiac disease. Genetic tests for celiac are helpful in many situations. Here are a couple of examples of when genetic testing may be used:
- When you have multiple signs and symptoms of celiac disease but the blood tests for celiac came back negative. You aren’t sure if you should pursue a biopsy or not. If you don’t have one of the genes, the biopsy would not be indicated, as it is highly unlikely that you have celiac.
- When you have multiple signs and symptoms of celiac disease, but you have already initiated a gluten-free diet and have experienced an improvement in your health and well-being. You don’t want to start eating gluten again simply to have blood tests and/or a biopsy.
- As a screening tool for family members of those who have celiac disease to identify those that would be at risk for celiac disease.
Trial Gluten-Free Diet
I do not recommend a trial of a gluten-free diet to be used as a part of the diagnostic process unless you are completely sure that you can use response to diet as your diagnosis. Once you go on a gluten-free diet and feel better, there’s often no turning back. Blood tests and biopsy depend on regular consumption of gluten for the three months prior to the test or biopsy. If you go on a gluten-free diet and feel better, you will need to start eating gluten again if you wish to pursue further celiac testing. This is an important consideration, as most people don’t want to start eating gluten again if they feel better on a gluten-free diet.
I fully support those who have already started a gluten-free diet and feel better and then come to me asking why. I have a client who started a gluten-free diet as a part of cleanse and felt immediate relief from a wide-range of non-specific complaints. She was too far into the gluten-free diet for diagnostic tests and she was struggling with the realization that she did not have a clear diagnosis of celiac and that no doctor would diagnose her without a positive blood test or biopsy. I recommended the genetic tests and she does have one of the celiac genes. Finally and fortunately, a local gastroenterologist did a complete assessment and diagnosed her with celiac based on the facts that she had a positive response to a gluten-free diet, signs and symptoms of celiac disease and a genetic marker for celiac.
Consult First, Gluten-Free Later
If you are suspicious of celiac disease, please consult with a knowledgeable medical practitioner before proceeding with any dietary changes. This is tricky and complicated stuff. There is not always a clear diagnosis of celiac disease and it’s not always a straightforward path. But, when possible, diagnosis of celiac is essential! More on that next time….
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