Screening for Celiac Disease can be done through both genetic and antibody tests. The genetic test will show if the genes necessary to develop the disease are present. This test is also good to rule out the disease. The antibody blood test will show if the system is responding negatively to gluten. In either case, a positive result requires further action for diagnosis. Diagnosis occurs only with an endoscopic biopsy.
Take home genetic cheek swab test kits are available through our office. It is necessary to see a doctor for the antibody screening test and full diagnosis. We have a free blood screening every October.
Antibody Testing
To help diagnose celiac disease, physicians first test blood to measure levels of certain antibodies. These antibodies are anti-endomysium and anti-tissue transglutaminase. A positive antibody test indicates only that a person needs a biopsy; it is not a diagnosis in and of itself. Antibody tests measure your immune system's response to gluten in the food you eat. Your doctor may order a panel of tests to aid in diagnosis, or order one or several to see if you may need further evaluation. The blood for these tests are usually sent to one of only a few labs in the country that are best suited for conducting the test and interpreting the results. These laboratories include Prometheus Labs and the Mayo Clinic.
What blood tests are needed to help diagnose Celiac Disease?
Researchers have discovered that people with celiac disease who eat gluten have higher than normal levels of certain antibodies in their blood. Antibodies are produced by the immune system in response to substances that the body perceives to be threatening. Think of antibodies as a sending out a warning signal to the body-only in the case of an autoimmune disorder like celiac disease, the warning signal sounds for something that is supposed to be safe-the proteins in wheat, rye and barley that are generically known as "gluten."
Which is the correct Screening Test?
Anti-Tissue Transglutaminase (tTG-IgA) -- A screening test is commonly used when an individual is in a risk group for Celiac Disease, whether or not he/she has symptoms. This test is usually the one offered for Celiac screening events, as it is the most sensitive test available.
Other Tests
Total Serum IgA -- This one tests for IgA deficiency, a condition which can affect the accuracy of an antibody test)
Anti-endomysial antibody test (EMA-IgA) -- EMA-IgA are very specific for Celiac Disease but they are not as sensitive as teh tTG-IgA.
HLA-DQ2 and HLA-DQ8 gene tests -- The "gene tests" are not antibodies. They can be used to exclude Celiac Disease (if negative) in doubtful cases.
Note:
Anti-gliadin antibodies (AGA-IgG and AGA-IgA) are no longer used to test for Celiac Disease due to a low level of accuracy in people who have not yet been diagnosed.
If my positive antibody test suggests I may have Celiac Disease, how do I find out for sure?
If antibody tests and/or symptoms suggest celiac disease, the physician needs to establish the diagnosis by obtaining tiny pieces of tissue from the small intestine to check for damage to the villi. This is done in an endoscopic biopsy procedure. The physician eases a long, thin tube called an endoscope through the mouth and stomach into the small intestine, and then takes samples of the tissue using instruments passed through the endoscope. Biopsy of the small intestine is the only way to diagnose celiac disease.
Why is it necessary to have the endoscopic biopsy?
It is important to know that the blood testing can only confirm that you do not have celiac disease. This is why the biopsy is necessary if your test results are positive, to confirm the results. It is important to definitively establish the presence of celiac disease and rule out the presence of other conditions, including food allergies, a far more common condition
What do I do if I have a negative blood test (or panel) but I'm still having symptoms?
While it is rare, it is possible for patients to have a negative antibody test results and still have celiac disease. IgA deficiency is one example where this could occur. Further medical evaluation is important for anyone who is still experiencing symptoms, to establish the diagnosis or to rule out celiac disease as a part of establishing another diagnosis
Genetic Testing
When an individual is diagnosed with celiac disease, the entire family learns that they must be tested on a regular basis for the condition. First degree relatives (parent, child, sibling) have a 1 in 22 chance of developing celiac disease in their lifetimes; in second degree relatives, (aunt, uncle, cousin, grandparent) the risk is 1 in 39. The Genetic Screening can rule out the disease, however, if the gene is present, lifetime regular screening can help family members reduce the long term impact of celiac disease and facilitate a quick diagnosis.
What is genetic testing and who can benefit from it?
There is a blood test or cheek swab test kit available to determine whether or not an at risk individual carries the genes responsible for the development of celiac disease. These genes are located on the HLA-class II complex and are called DQ2 and DQ8. Each case of celiac disease has been found to show these so-called "haplotypes"; therefore, a negative gene test indicates that celiac disease cannot develop in that individual.
There are two main reasons for using the genetic test when evaluating an individual for celiac disease. The first case is to "rule out" celiac disease, which is a medical term that indicates an individual does not possess a necessary risk factor for the development of celiac disease, genetic predisposition. Without this factor, it is impossible that the individual with a negative gene test will develop celiac disease in the future. People who test negative for the gene would not be required to have regular antibody screening for the remainder of their lives. For example, the children of an adult with celiac disease could have the gene test. The results would allow the parent to know which children need close monitoring.
In individuals with symptoms who have not had a biopsy to diagnose celiac disease, but have been on the gluten-free diet for a significant period of time, the gene test is often the only way to determine if symptoms could possibly be related to celiac disease. For a person who faces this situation, a negative gene test would indicate that symptoms are not the a result of celiac disease. A positive gene test, however, does not diagnose the disease but increases the likelihood that it is present.
If I have a gene for Celiac Disease, does that mean I have Celiac Disease?
The gene test does not diagnose celiac disease. It places an individual into an "at-risk" group for celiac disease, which indicates the individual should be closely monitored with antibody testing in the future. When the genetic predisposition for celiac disease was detected (on Chromosome 6) researchers noted that the genes were a necessary but not sufficient condition for the disease to develop. In fact, up to one third of the U.S. population has the genes for celiac disease, new research shows a significant portion of those people will develop the disease at some point in their lifetime.
How is genetic testing different from antibody testing for Celiac Disease?
The blood tests that most people with celiac disease are familiar with are the antibody tests. These tests, such as the tissue transglutaminase test (tTG) or the antiendomysial (EMA) antibody test, measure the autoimmune response triggered by gluten that occurs at a point in time. (Think of it as a photograph.) These are important tests because they characterize the extent to which the immune system is responding to gluten.
Unlike antibody testing, the HLA gene testing for celiac disease measures the presence or absence of genetically-programmed molecules that are found on the surface of some cells. The HLA gene test for celiac disease can be performed at any time after birth (and even in the cord blood at birth!)-an individual is either born with or without these factors and they do not change over time.
How is the genetic predisposition for Celiac Disease Inherited?
Inheriting the genes for celiac disease occurs differently than the manner in which many genetic traits are passed on. We are accustomed to thinking in terms of dominant or recessive genes which are inherited from both parents and form sets to determine hair color, height, and other human health characteristics. In fact, even though DQ2 and DQ8 are passed on similarly, they are not sufficient to determine the occurrence of the disease, even if they are present in double doses.
Because 35% of the American population have either DQ2 (more commonly) or DQ8, it is possible for two affected people to marry each other. The genes can be passed on by males as well as females. Therefore, one person's gene test doesn't necessarily mean that the other side of the family is not affected as well.
Who can order the gene test? Does it have to go to a special laboratory? How much does it cost?
The University of Chicago Celiac Disease Center distributes take home test kits from Kimball Genetic. The tests can be submitted directly or through your doctor. Insurance companies are increasingly covering some or all cost for the test. Call our office if you'd like us to send you a kit. The fee to process the test of approximently $400.
Follow-Up Testing
What does follow up testing do?
Follow-up testing is conducted to ensure that antibody levels are returning to normal, indicating that the intestine is healing on the new diet. For this reason, repeat intestinal biopsies are no longer necessary. These tests also indicate the extent to which a celiac is avoiding gluten, and can detect when hidden gluten has entered the diet
How often should follow up testing occur?
New celiacs should receive follow-up testing twice in the first year after their diagnosis. The first appointment should occur three to six months after the diagnosis, and the second should occur after 1 year on the gluten-free diet. After that, a celiac should receive follow-up testing on a yearly basis.
What tests are needed to follow up appointments? How are they interpreted?
New guidelines on the diagnosis and treatment of celiac disease by the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition state that tTG-IgA testing should be used for follow-up care. Interpreting this test result is straightforward-a celiac on the gluten-free diet should have a negative test. The numerical value of the test is not important.
Follow Up Test #1
tTG-IgA: This test result should be negative
The numerical value of the test doesn't matter as long as the result is negative.
The University of Chicago Celiac Disease Center recommends additional testing, because the tTG test can sometimes be inaccurate in people with autoimmune disorders like Type 1 diabetes and thyroid disease. In addition, the tTG can sometimes become negative before a celiac has actually experienced significant healing.
For these reasons, Anti-Gliadin Antibodies (AGA) are also important. There are two types that need to be run: AGA-IgA, and AGA-IgG. In this circumstance, the numerical values of the tests are very important. The numbers should be as close to zero as possible, indicating a minimal antibody response to gluten. The additional advantage of these tests is that the blood can be drawn by any physician and sent to any laboratory.
Follow Up Test #2
Anti-gliadin IgA: This result should have a very low negative value
In this case, the numerical value does matter because a high negative test result still indicates that a patient is eating gluten. A low negative indicates that the diet is working well.
I was diagnosed 15 years ago and have never received follow up testing. Why should I start now?
It's never too late to begin follow up testing and to learn from the results. Food manufacturing practices change often, and even the most diligent celiac cannot keep up with all the changes. In addition, some celiacs find that current health problems may be related to celiac disease, such as anemia or bone density. The reverse is also true-some find that current health problems they've attributed to celiac disease aren't related, because their antibody levels indicate that celiac disease isn't active. In either case, the patient and physician have received valuable information.
While follow-up testing is especially important for people in the first five years after diagnosis (this is when the most serious complications of celiac disease can occur) testing can help all celiacs know that they are doing well with the diet or need to make changes to protect their health.
I worry that I might be feeding my child the wrong foods and I can't tell if her stomach aches are from Celiac Disease or something else?
For concerned parents, and for anyone who worries if they are making the right food choices for themselves or their child, follow-up testing can be very helpful. Negative test results reinforce that the family's approach to a child's gluten-free diet is working well.
I've been having joint pain and I think it's from Celiac Disease. I follow the diet very carefully.
Follow up testing is important, and can be performed when there is a question about whether or not a health condition, like joint pain, could be related to celiac disease. A series of positive antibody tests (indicating gluten in the diet) may indicate that a complication of celiac disease exists, in this case, joint pain. When antibody tests are negative, indicating a strong level of compliance with the diet, it is unlikely that celiac disease is contributing to the worrisome symptom. While this is not an exact science, follow up testing can often clarify whether or not a health condition could be a complication of celiac disease.