Genetic Testing for Celiac Disease Help Confirm a Diagnosis

Dr. Sheila Crowe, a professor at the University of Virginia, recently joined the Consults blog to answer reader questions about celiac disease.

Dr. Crowe responds to readers asking about the disease running in families, genetic tests that may help confirm a diagnosis, food allergies and thins that set off the ailment.

Which Groups Are at Highest Risk for Celiac Disease?

Q.Is it true that Irish ancestry gives you a higher predisposition to the gene?

A.Dr. Crowe responds: When I went to medical school in Canada three decades ago, we did learn about celiac disease, including that celiac disease was most common in the Irish population, with about 1 in 300 people affected. At that time, celiac disease was thought to occur in 1 in 2,000 Canadians, similar to the rates in Australia and New Zealand. That figure was less than in most northern European countries but much greater than in the United States, where the frequency was estimated to be 1 in 5,000. When I first moved to the United States, in 1992, I was surprised that few of my colleagues knew much about celiac disease.

Since that time, things have really changed in terms of what is known about who gets celiac disease and how common it is. We now know that celiac disease occurs in many as 1 in 100 people in nearly every country in Europe, including the Mediterranean region, as well as in North Africa and Asia from the Middle East to as far east as India and in countries settled by migrants from countries where celiac disease occurs.

What many of our readers may not know is that only 10 percent to 15 percent of those with celiac disease have actually been diagnosed in the United States. The rate is probably equally low in many other countries. In some countries like Finland, national health policies have increased the detection rate of celiac disease to about 50 percent.

So, Kate, what you have heard about the Irish having a higher disposition to celiac disease is true, but it turns out that many people in the countries or regions I mention above also have the genes that predispose to celiac disease. These genes are in the family of genes for proteins referred to as human leukocyte antigens, or H.L.A. A subset of these genes are involved in autoimmune diseases, and the genes that predispose to celiac disease are in that group.

Some of these H.L.A. genes can be tested for using a sample of blood or cells taken from your mouth by swabbing the inside of your cheek. They are known as H.L.A. DQ2 and H.L.A. DQ8; 95 percent of people with celiac disease have genes that include H.L.A. DQ2, and 5 percent have genes with H.L.A. DQ8.

Tests that detect H.L.A. DQ2 and DQ8 genes can suggest a diagnosis of celiac disease, but they cannot confirm a diagnosis, since 35 percent to 40 percent of the overall American population carries these genes. Only a small subset – 2 percent to 3 percent — of all people with these genes will ever get celiac disease.

What this test can tell you is whether you are at risk of having celiac disease, since without these genes it is virtually impossible to get celiac disease. This is one celiac disease test that only needs to be checked once in a lifetime, since our genetic makeup does not change. (In contrast, antibody blood tests for celiac disease can be negative when first checked but become positive later in life when celiac disease starts to develop; see my earlier post, “Confirming a Diagnosis of Celiac Disease.”

In addition, only about 40 percent of the risk of celiac disease can be attributed to these H.L.A. genes. We believe that other genes, as well as environmental factors, lead to celiac disease. So far, scientists have identified over a dozen possible non-H.L.A. genes that may be associated with celiac disease, but whether these genes actually play a role remains to be seen.

Thanks, Kate, for your question.

Easy Genetic Tests for Celiac Disease?

Q.Is there an easy genetic test for celiac disease? My doctors have said that I may have it and they just can’t find it. My blood test is negative, and my colonoscopy and endoscopy were negative. However, as the doctor said, they couldn’t get through where my appendix is to see the area there. I have rashes and classic symptoms, but the elimination diet and challenges from the Prince Alfred Hospital Sydney have been inconclusive, not to mention boring. A genetic test would be so easy, and here they are free on the universal health care system.

A.Dr. Crowe responds: The H.L.A. DQ2/DQ8 genetic test, which I discussed above, would help out in your case, Serena, since it would let you know if you have the genetic predisposition to celiac disease. If you don’t have these genes, then you won’t have to worry about having celiac disease and other medical conditions can be considered as a cause of your problems. It appears you live in Australia — I expect this genetic test is available there.

Celiac Disease vs. Food Allergies

Q.I was diagnosed with celiac about 10 years ago using IgE. I also had an intestinal biopsy done which was inconclusive. After being gluten-free for seven years, I went off my diet and have been doing just fine for three years. My primary care physician says that so long as I don’t feel bad I can eat gluten with abandon. My IgE levels are sky high again, but I’m conflicted as I’m feeling really just fine. I don’t live in a black and white world, but I am nervous that I’m setting myself up for permanent damage down the road. Please help!

A.Dr. Crowe responds: Andrea, your query intrigues me, given my interest in celiac disease and also food allergies.

I am not sure if you really mean IgE, since IgE antibodies are not involved in celiac disease. As I discussed earlier this week in “Confirming a Diagnosis of Celiac Disease,” IgA and IgG are the two types of antibodies that are used in checking for possible celiac disease. IgE antibodies to various foods are typically measured in the blood or by skin prick testing when food or other allergies are suspected.

If you had an allergy to wheat and not celiac disease, then your doctor may be correct in letting you eat wheat again. When it comes to food allergies that involve IgE antibodies, unless one has a clinical reaction to that antigen — be it wheat, cow’s milk proteins like casein or beta-lactoglobulin, or any other food protein — then it isn’t always necessary to avoid that food, even if the skin prick test or blood test is abnormal. However, when it comes to celiac disease that has been biopsy proven, even eating a small amount of gluten can lead to problems without your necessarily feeling unwell. It can take months to years for some patients with celiac disease who start eating gluten after being gluten-free for a long time to get sick again.

I would recommend verifying which blood test you have had checked. Was it an antibody to the protein found in wheat, or to TTG or gliadin, the proteins involve din celiac disease? In addition, what type of antibody was it: IgA, IgG or IgE?

If it turns out you have elevated celiac disease antibodies (IgA or IgG) to TTG or gliadin, you may want to check into why your intestinal biopsy was inconclusive by getting an expert pathologist to look at a set of your biopsy slides. If, after all this, there is still some doubt about a diagnosis of celiac disease, then the H.L.A. DQ testing which I discussed earlier in my replies to Kate and Serena would be helpful. If you test negative for H.L.A. DQ2 or DQ8, then you don’t need to worry about having celiac disease or damaging your intestine if you keep eating wheat.

Do a Rash of Symptoms Point to Celiac Disease?

Q.I have had many health problems for the last 35 years, since I was in my early 20s. I’ve gone to many doctors, having multitudes of tests during that time. Not one doctor has even suspected celiac.

After more than 20 years, I did start to get some diagnoses: fibromyalgia, chronic fatigue, I.B.S., iritis, diabetes, high blood pressure, cardiac artery disease (two heart attacks in 2004, resulting in three stents in my heart), osteoarthritis, depression, sleep apnea, obesity ….

My symptoms are varied: neurological (several doctors have thought I had M.S., but no lesions – memory loss, fuzzy thinking, numbness, muscle tics, drop foot, droopy eye). Dry mouth, eyes and skin; very high inflammation levels, extreme fatigue, diarrhea/constipation, stomach cramps, bloating, vomiting, swollen and painful joints, changes in my nails, ringing in my ears, muscle pain, skin rashes and probably more that have slipped my mind!

My question is this: When I suspected that gluten was a problem for me and went on a G.F. diet, many of these symptoms went away. I have energy, think clearer, am losing weight, and my fingers and ankles don’t hurt or swell anything like they used to. Do my systemic symptoms and “G.F. cure” tend to lean toward celiac disease? What is the benefit of knowing for sure? I will not go back on a gluten control. This last bout was too much for me!

Thanks for any help you can give me.

Becky Goodnight

A.Dr. Crowe responds: I completely understand your perspective, Becky, and this is another situation in which the genetic test can be of some help. Knowing whether you have celiac disease can also help determine whether your family might also be at risk.

If you do not have the H.L.A. DQ2 or DQ8 genes, then it is very unlikely that you have celiac disease. Your family members are also not at increased risk.

If you don’t have celiac disease susceptibility genes, your response to the gluten free diet may be due to another condition, such as gluten sensitivity or perhaps one of a few other conditions that sometimes improve on a gluten-free diet. As many of our readers are aware, the gluten free diet often eliminates other substances in addition to gluten that can cause health problems, since fewer processed foods and more natural foods are consumed.

If you do have H.L.A. DQ2 or DQ8 genes, then you could have celiac disease, but as noted above, this test cannot confirm a diagnosis. Given your story, Becky, I would not recommend going back on gluten (a gluten challenge) to try to confirm the diagnosis. My only suggestion would be to make sure that you have been tested for possible causes of your medical problems other than celiac disease.

Gluten-Free Children?

Q.Had my son tested yesterday (celiac blood panel) and waiting to see if he has celiac. He is showing some symptoms, so I removed gluten from his diet. It is genetic, isn’t it?

Allison
 

A.Dr. Crowe responds: I have taken the liberty of extracting this one question from your longer posting, Allison, where you described your own celiac disease. Yes, celiac disease does have a genetic basis; your son has a 50 percent chance of inheriting your H.L.A. genes. However, as I’d discussed in an earlier posting (see “Diagnosing Celiac Disease on a Gluten-Free Diet”), it is not recommended that anyone go on a gluten-free diet until the diagnosis of celiac disease is made.

I am interested to know what your son was tested for, and maybe you will have the results by now. Ideally, relatives of a patient with celiac disease who themselves have symptoms suggesting celiac disease should get both the genetic test and an antibody test, typically a TTG IgA level and also a AG IgA level if the relative is a young child.

What are the possible scenarios? If your son does not have the H.L.A. DQ genes that place him at risk, then you don’t have to worry about him getting celiac disease. He did not inherit your celiac disease H.L.A. genes.

If your son has the H.L.A. DQ2 or DQ8 susceptibility genes but his antibody levels are negative, with a normal total IgA level, then he will need to have antibodies, especially a TTG IgA level, checked periodically, since he is at risk of developing celiac disease later in life. If he has an elevated celiac disease antibody test now, then I expect his doctor will recommend confirming celiac disease with intestinal biopsies.

Please let me know how this story turns out, and whatever happens, I wish you and your son the best.

A 7-Year-Old With Stomach Pains

Q.My 7-year-old always has a stomachache, sometimes severe, after he eats. He also has a long history of constipation. I thought that he was lactose intolerant, but he seems to have tested negative for that. He also was tested for celiac over a year ago, but that came back negative too. My questions are the following:

Should I have him retested for celiac disease, and if so, which tests should I absolutely make sure his doctor requests?

Also, if someone tests negative for celiac, could the person actually have the disease but just not be testing for it?

I also forgot to mention in my post above that my 7-year-old was found to be extremely iron deficient, yet he has a diet rich in iron, both meat and plant based. Could this be a sign of celiac if coupled with his severe stomach pains?

abs

A.Dr. Crowe responds: I would definitely recommend that your son be retested for celiac disease, and make sure that he gets a TTG IgA test along with the total IgA level if this latter test was not checked previously.

As I discussed in my reply to Karen in an earlier posting, “Confirming a Diagnosis of Celiac Disease,” there are situations in which it is advisable to proceed with an endoscopy, even if the antibody tests are negative. This is a bigger decision to make when children are involved, but given your son’s problems (abdominal pain, iron deficiency and altered bowel habits – yes, constipation can occur in celiac disease), I would be tempted to recommend this procedure even if his antibody tests come back negative.

If he has IgA deficiency and the antibody tests are negative, this would be further reason to consider an endoscopy to take intestinal biopsies. If there is any hesitancy on anyone’s part, checking the genetic test could be the deal breaker, since if your son has celiac disease susceptibility genes, then I would go for an endoscopy. Of course, other conditions that could be a cause of his problems, like Crohn’s disease, should be checked for if this has not already been done. I hope a cause and treatment for your son’s problems are found soon.

When Celiac Disease Runs in the Family

Q.Wow, I just read all the posts so far. It’s amazing how much confusion there is about this subject. My mother, in her 70s, was suffering from what seemed to be a wasting disease after a lifetime of good health and fitness. After three years of the same tests and no explanation (going back to the same doctor!), she went to a hospital gastro clinic, where she was diagnosed with celiac sprue in 1996. By the way, I don’t think there’s a difference between the Canadian and American medical systems when it comes to this.

Then we learned that my maternal uncle had suffered from unrecognized celiac disease in early childhood, with many classic symptoms occurring all his life because he never altered his diet. Even after he died, his wife never mentioned it, as I guess no one realized it is genetically inherited. Two of my sisters tested positive for gluten antibodies, but I have not. I have always assumed that celiac sprue is what you get if you are gluten intolerant and all the villi in your small intestine get wiped out.

Rather than paying every year for the antibody testing, I opted for the genetic test two years ago and found I possess both genetic markers of gluten intolerance. Having seen what celiac disease did to my mother, who never fully recovered at her advanced age, I have opted to be on a gluten-free diet for the rest of my life “just in case.” It’s fine by me most of the time, unless I’m traveling or eating out. Since I’ve never had symptoms, I will cheat occasionally rather than go hungry or risk offending a well-meaning host.

I had to be persistent with my (older) doctor, an internist, to take a serious interest in this issue. To his credit he did, or I would have found someone else young enough to have come through med school in the past 10 years to order the tests.

Sandra

A.Dr. Crowe responds: Thanks for your perspective, Sandra, and I agree that delayed diagnoses of celiac disease occur in both Canada and the United States. Delays of a decade and more have been reported from support groups in both countries. I am probably one of the “older” doctors you refer to but, to be fair, I did learn about celiac disease in medical school. I suspect that information met more receptive ears since I had married someone with celiac disease before entering medical school and his mother had co-founded the Canadian Celiac Association in 1972.

I have included your posting in this section on “Genetic Testing in Celiac Disease” since you used the result of this test to decide whether you would start on a gluten-free diet or not. While I do not always recommend that someone start a gluten-free diet based on the genetic test alone or even antibody testing without intestinal biopsies, as I discussed in the posting “Confirming a Diagnosis of Celiac Disease,” I think your reasoning and family experiences led you to make a rationale decision to eat “gluten-free.”

I do discourage families from making such a decision for their children based only on family history or a positive genetic test, since a gluten-free is difficult to adhere to, has some inherit nutritional deficiencies and can be more expensive. Not everyone with the genes or a family history will develop celiac disease – the chance of this happening if you have the “right” H.L.A. genes is 20 percent to 30 percent.

A Daughter With Symptoms of Celiac Disease

Q.About 15 years ago I suspected that my husband had a sprue and fought with his (Navy Medical) Doctor to have an upper G.I. done. The results came back positive. He was 43, severely underweight, yellowed eyes, severe and chronic diarrhea, fatigued and had been eating over 4,000 calories a day to keep his energy up.

Trials and tribulations later, we buy most of his gluten free foods at Trader Joe’s here in San Diego. We have learned to reread labels and to ask specific questions regarding wheat/gluten in products and restaurants.

After our daughter turned 5, we had her tested for celiac disease. She was already lactose intolerant by testing and symptoms. The results were negative.

Today, at 22, she still is bothered by a chronic diarrhea and stomach cramps. The similar complaints as if she ate milk products, but as she states not all milk products bother her.

If her insurance permits, should we have her retested for celiac disease? At her first test she only was reactive to one of the two antibodies. Can one grow more antibodies?

Given the probability of the disease, shall she just go gluten free? I’ve read there are a number of levels of gluten sensitivity.

How much is known about the genetics of this disease? Can she pass this to her kids? And what are the odds?

Thanks.

Laurie

A.Dr. Crowe responds: Laurie, I am glad to hear that in spite of a rocky start, your husband was diagnosed and treated for celiac disease. I can fully understand why you don’t want your daughter to run into the same type of problem. I am not sure what testing she had when she was 5, but I would bet that it was not a genetic test, since these have only been available for more routine use in the past five years or so.

Given the family history and her symptoms, I would recommend that she get both the genetic test and the TTG IgA test with a total IgA. I certainly hope her insurance company will cover these costs, since making a diagnosis of celiac disease and getting her started on a gluten-free diet now if she does have celiac disease could save them money in the long run, as your husband’s medical history makes clear. As I have mentioned in other replies in today’s posting on genetic testing yes, the antibodies can become positive over time in both children and adults.

As I discussed at the start of this posting a fair amount is known about the HLA DQ2 and DQ8 genes and yes, if your daughter has these susceptibility genes, she could pass them on to her children.

Late-in-Life Onset of Celiac Disease

Q.My father was diagnosed with celiac disease about 12 years ago, as well as his sister and her son. My brother and I had the blood test done, and neither of us had the abnormal reading. I am wondering whether celiac could still present itself later in life? I’ve heard that hormonal changes such as pregnancy can trigger the onset of the disease, and I’m curious if that’s true.

Mary S.

A.Dr. Crowe responds: Mary, I am guessing that the blood test you and your brother had was the TTG IgA test. As we discussed in the posting “Confirming a Diagnosis of Celiac Disease,” this test is not always accurate. In addition, it can turn positive later in life if you are genetically predisposed to celiac disease. I would therefore suggest that you get the HLA DQ2/DQ8 testing performed. If you have the genetic predisposition, then re-checking celiac disease antibodies is worthwhile.

We don’t really know why celiac disease shows up later in life in some folks. Pregnancy, stress, infection, gastric surgery and a few other things have been suggested as possible triggering factors. The average diagnosis of celiac disease is now made in 40 or 50 year olds, whereas it used to be a disease of children. Patients are being diagnosed as late as the eighth decade of life and later. More research needs to be done to determine why celiac disease is presenting later in life and why it is a more common condition than in the past.