Celiac Disease
Celiac disease has been known by many different names in the medical literature over the years, including gluten-sensitive enteropathy and celiac sprue (to differentiate it from tropical sprue). CELIAC DISEASE can be defined as a permanent intolerance to the gliadin fraction of wheat protein and related alcohol-soluble proteins (called prolamines) found in rye and barley. CELIAC DISEASE occurs in genetically susceptible individuals who eat these proteins, leading to an autoimmune disease, where the body’s immune system starts attacking normal tissue. This condition continues as long as these food products are in the diet.
The resulting inflammation and atrophy of the intestinal villi (small, finger-like projections in the small intestine) results in the malabsorption of critical vitamins, minerals, and calories. Signs and symptoms of the disease classically include diarrhea, short stature, iron-deficiency anemia and lactose intolerance. However, many patients will also present with “non-classical” symptoms, such as abdominal pain, “irritable bowel”, and osteoporosis. Patients may also be screened for celiac disease because of the presence of another autoimmune disease, such as type I diabetes or thyroid disease, or a family history of celiac disease, without having any obvious symptoms. Serum antibodies can be utilized to screen for celiac disease. However, the key to confirming the diagnosis remains a small intestinal biopsy, and the patient’s subsequent clinical response to a gluten-free diet. Clinicians in the United States must maintain a high index of suspicion for this disease, as it is significantly under-diagnosed in this country.
What is a wheat allergy?
People can also have other medical problems, besides celiac disease, when they eat wheat and related proteins. Wheat allergy is one of the top 8 food allergies in the United States. Allergic reactions after eating wheat may include reactions in the skin, mouth, lungs, and even the GI tract. Symptoms of wheat allergy can include rash, wheezing, lip swelling, abdominal pain and diarrhea. The branch of the immune system activated in allergic reactions is different from the branch thought to be responsible for the autoimmune reactions of celiac disease.
What is gluten intolerance?
People can also experience’ intolerance’ to gluten. Food intolerances are not thought to be immune mediated. GI symptoms with wheat or gluten intolerance may include gassiness, abdominal pain, abdominal distension, and diarrhea. These symptoms are usually transient, and are thought NOT cause permanent damage.
Patients with lactose intolerance, where the lactose sugar in diary products is not digested well, may also experience gassiness, abdominal pain, abdominal distension, and diarrhea. Like gluten or wheat intolerance, these symptoms will pass once the lactose is out of the person's system, and will not cause permanent damage.
Why is it important to know if you have celiac disease, versus wheat allergy or gluten intolerance?
Celiac disease, wheat allergy and gluten-intolerance are treated similarly, in that patients with these conditions must remove wheat from their diet. It is important to note, however, that there is a difference between these three medical problems.
Celiac disease is an autoimmune condition, where the body's immune system starts attacking normal tissue, such as intestinal tissue, in response to eating gluten.
Because of this, people with celiac disease are at risk for malabsorption of food in the GI tract, causing nutritional deficiencies.
This can lead to conditions such as iron deficiency anemia and osteoporosis.
Since a person with wheat allergy or gluten-intolerance usually does not have severe intestinal damage, he or she is not at risk for these nutritional deficiencies.
Celiac disease is an autoimmune condition, putting the patient at risk for other autoimmune conditions, such as thyroid disease, type I diabetes, joint diseases and liver diseases.
Since wheat allergy and gluten intolerance are not autoimmune conditions, people who have food allergies and intolerances are not at increased risk to develop an autoimmune condition over the general population's risk. And finally, celiac disease involves the activation of a particular type of white blood cell, the T lymphocyte, as well as other parts of the immune system.
Because of this, patients with celiac disease are at increased risk to develop GI cancers, in particular lymphomas. Because food allergies and intolerances do not involve this particular immune system pathway, and do not cause severe GI tract damage, these patients are not at increased risk for these cancers.
Thus, while celiac disease, wheat allergy, and gluten-intolerance may be treated with similar diets, they are not the same conditions. It is very important for a person to know which condition they have, as the person with celiac disease needs to monitor himself or herself for nutritional deficiencies, other autoimmune diseases, and GI cancers. In general, the symptoms from food allergies and intolerances resolve when the offending foods are removed from the diet and do not cause permanent organ damage.
Diagnosing Celiac Disease
What are the appropriate screening tests for celiac disease?
The tests of choice are antibody measurements in the blood, ideally performed before the patient has removed gluten from the diet. However, patients and physicians must remember that no screening test is perfect, and that the keys to confirming the diagnosis of CELIAC DISEASE remain a small intestinal biopsy combined with the patient’s subsequent clinical response to a gluten-free diet. Thus, a patient (especially a young child) with symptoms of CELIAC DISEASE should have a small bowel biopsy, even if the antibodies are not highly suggestive.
What are the different antibody tests available? Can there be errors in testing?
The blood tests can be divided into 2 different types of antibodies: those which are “anti-gluten”, and those that “anti-self”. The “anti-gluten” antibodies are the anti-gliadin IgG and IgA. Ig stands for “immunoglobulin” or “antibody”. The “anti-self” antibodies are anti-endomysial IgA and anti-tissue transglutaminase IgA. The tissue transglutaminase IgA antibody is often abbreviated as “tTG”. Each antibody test varies widely in its sensitivity and specificity for predicting whether the disease is present in any individual. It must be remembered that NO test in medicine is correct 100% of the time in each person!
There are also several conditions which may yield false negative antibody results. A false negative means that the patient actually has the disease, but the test result is negative. One of the conditions that may give a false negative result is Immunoglobulin A or IgA deficiency. If a patient has a low total IgA level, the antibodies may be falsely low. This is why I always recommend that a patient have a total IgA level drawn at the same time the antibody testing is done. Young children may not make the some of the “anti-self” antibodies, as it takes a somewhat mature immune system to make them. So in a young child, antiendomysial antibody, or the TTG antibody, can have false negative results. An inexperienced lab can misread the anti-endomysial IgA test, which requires someone to read a slide through a special microscope. It is possible that a celiac patient could have a positive antibody test at one lab, and a negative test at another. This is because different labs may use different commercial test kits, which vary in their sensitivity and specificity. And lastly, a person has to be ingesting gluten at the time the antibodies are drawn. A gluten-free diet will make the antibody tests negative.
Let’s discuss the different antibodies and what the strengths and weaknesses are for each.
Antigliadin antibodies
The antigliadin antibodies IgG and IgA recognize a small piece of the gluten protein called gliadin. These antibodies became available during the late 1970’s and were the first step towards recognizing CELIAC DISEASE as an autoimmune disorder. Antigliadin IgG has good sensitivity, while antigliadin IgA has good specificity, and therefore their combined use provided the first reliable screening test for CELIAC DISEASE. Unfortunately, many normal individuals without CELIAC DISEASE will have an elevated antigliadin IgG, causing much confusion among physicians. The antigliadin IgG is useful in screening individuals who are IgA deficient, as the other antibodies used for routine screening are usually of the IgA class. It is thought that 0.2-0.4% of the general population has selective IgA deficiency, while 2 to 3% or more of celiacs are IgA deficient.
If a patient’s celiac panel is only positive for antigliadin IgG, this is not highly suggestive for CELIAC DISEASE if the patient has a normal total IgA level, corrected for age. Younger children make less IgA than older children and adults. A markedly elevated antigliadin IgG, such as greater than three to four times the upper limit of normal for that lab, is highly suggestive of a condition where the gut is leakier to gluten. This can happen in food allergies, cystic fibrosis, parasitic infections, Crohn’s disease, and other types of autoimmune GI diseases. These antibodies may also be slightly elevated in individuals with no obvious disease.
A strength of the antigliadin antibodies is that they are ELISA tests. ELISA is an abbreviation for “enzyme-linked immunosorbent assay”. This is a rapid immunochemical test that involves an enzyme, which a protein that causes a biochemical reaction. An ELISA test also involves an antibody or antigen. ELISA tests are utilized to detect substances that have antigenic properties, primarily proteins, such as gliadin. The importance of an ELISA test is that is it rapid, inexpensive, and run by a machine. Thus the results are independent of observer variability. The TTG test is also an ELISA test. This is in contrast to the antiendomysial IgA, where a slide has to be made, and a person has to look at it through a microscope. These are more prone to human error.
Antiendomysium antibodies
The antiendomysial IgA antibody is an excellent screening test for CELIAC DISEASE, with both a high sensitivity and specificity. It is considered the gold standard of antibodies. However, the subjective nature of this test (someone still needs to look at the slide under a microscope) may lead to false negative values and unacceptable variability between laboratories. This antibody was discovered in the early 1980’s, and rapidly gained use as part of a screening “celiac panel” by commercial labs in combination with antigliadin IgG and IgA. Its major drawbacks are that it may be falsely negative in young children, in patients with IgA deficiency and a lesser degree of villous atrophy, and in the hands of an inexperienced laboratory.
Tissue transglutaminase antibodies or TTG
Since tTG had been first described as the autoantigen of celiac disease in 1997, it has been utilized to develop innovative diagnostic tools. The tTG IgA ELISA test is highly sensitive and specific. The tTG assay correlates well with EMA-IgA and biopsy. However, it represents an improvement over the antiendomysial antibody assay because it inexpensive, rapid, is not a subjective test, and can be performed on a single drop of blood using a dot-blot technique. One negative aspect of the TTG antibody is that it can be falsely positive in a patient who has another autoimmune condition. TTG false positivity has been described in patients with both type I diabetes and autoimmune hepatitis. Theoretically, it can also be falsely positive in other autoimmune disease.
Treatment
Celiac Disease (CD) is a life-long digestive disorder found in individuals who are genetically susceptible. Damage to the small intestine is caused by an immunologically toxic reaction to the ingestion of gluten. This does not allow food to be properly absorbed. Even small amounts of gluten in foods may affect those with celiac disease and cause health problems. Damage can occur to the small bowel even in the absence of symptoms.
This is a a simple overview of the Gluten-Free (GF) diet. Not all areas of the diet are as clear-cut as portrayed by this Guide. This is intended to be used as a safe and temporary survival tool until the newly diagnosed celiac obtains additional information. Understanding these dietary requirements will enable the newly diagnosed to read labels of food products and determine if a product is GF.
Gluten is the generic name for certain types of proteins contained in the common cereal grains wheat, barley, rye and their derivatives.
ALLOWED Grains/Flours
Rice, corn (maize), soy, potato, tapioca, beans, garfava, sorghum, quinoa, millet, buckwheat, arrowroot, amaranth, teff, Montina®, flax, and nut flours.
NOT ALLOWED in any form
Wheat (enkorn, durum, faro, graham, kamut, semolina, spelt), rye, barley and triticale.
Frequently overlooked foods that may contain gluten and need to be verified:
Breading, Coating mixes, Panko Brown rice syrup
Croutons Energy Bars
Flour or cereal products Imitation bacon
Imitation seafood Marinades
Pastas Processed luncheon meats
Sauces, gravies Self-basting poultry
Soy Sauce or soy sauce solids Soup bases
Stuffings, Dressing Thickeners (Roux)
Communion wafers Herbal supplements
Nutritional supplements Vitamins & mineral supplements
Prescription Drugs Over-the-counter medications
Play-doh: a potential problem if hands are put on or in the mouth while playing with play-doh. Hands should be washed immediately after use.
Distilled alcoholic beverages and vinegars are gluten-free. Distilled products do not contain any harmful gluten peptides. Research indicates that the gluten peptide is too large to carry over in the distillation process. This leaves the resultant liquid gluten-free. Wines are gluten-free. Beers, ales, lagers, and malt vinegar are made from gluten-containing grains and are not distilled, therefore they are not gluten-free.
IF IN DOUBT -- GO WITHOUT!
When unable to verify ingredients or the ingredient list is unavailable DO NOT EAT IT. Regardless of the amount eaten, it is not worth triggering your immune system and the damage to the small intestine that occurs every time gluten is consumed, whether symptoms are present or not. A person with celiac disease may have additional food sensitivity not related to gluten.
WHEAT FREE IS NOT GLUTEN-FREE
Products labeled Wheat-Free are not necessarily gluten-free. They may still contain rye or barley-based ingredients that are not GF. Spelt is a form of wheat and is not acceptable on a gluten-free diet.
Contamination in Food Preparation
When preparing gluten-free foods they must not come in contact with food containing gluten. Contamination can occur if foods are prepared on common surfaces, or with utensils that are not thoroughly cleaned after preparing gluten-containing foods. Using a common toaster for GF bread and regular bread is a major source of contamination. Flour sifters should not be shared with gluten-containing flours. Deep fried foods cooked in oil shared with breaded products should not be consumed. Spreadable condiments in shared containers may also be a source of contamination. When a person dips into a condiment a second time, with the knife (used for spreading), the condiment becomes contaminated with crumbs (e.g. mustard, mayonnaise, jam, peanut butter, and margarine).
Wheat flour can stay airborne for many hours in a bakery (or at home) and contaminate exposed preparation surfaces and utensils or uncovered gluten-free products. Likewise, foods not produced in a gluten-free environment have the potential to be contaminated with gluten. This may occur when machinery or equipment is inadequately cleaned after producing gluten-containing foods. Food manufacturers are required to abide by Good Manufacturing Practices outlined in the FDA’s Code of Federal Regulations, to reduce the risk of contamination in manufacturing. Let common sense be your guide.
Like anything new, it takes time to adjust to the GF diet. It is natural to mourn old food habits for a short time. Stay focused on all the foods you CAN eat. Fresh fruits and vegetables are delicious and healthy. Fresh poultry, fish, meat and legumes provide protein and are naturally GF. Most dairy foods can also be enjoyed providing you are not lactose intolerant. GF substitutes for foods commonly made with wheat are available at health food stores and from GF food manufacturers. Try GF waffles for breakfast; a sandwich on GF bread for lunch; and rice, corn or quinoa pasta for dinner. Your new way of eating is very satisfying!
The GF diet is a life-long commitment and should not be started before being properly diagnosed with CD/DH. Starting the diet without complete testing is not recommended and makes diagnosis difficult. Tests to confirm CD could be inaccurate if a person were on a GF diet for a long period of time. For a valid diagnosis gluten needs to be reintroduced. Celiac Disease is an inherited autoimmune disease. Screening of family members is recommended. Consult your doctor for testing.
