Coeliac / Celiac Disease technical Diagnosis

Celiac Disease technical Diagnosis

Another article on this site discusses the myriad of possible symptoms associated with coeliac disease (CD). While we are a gluten free site and recommend eating a gluten free diet for celiacs, gluten intolerant people and just for general better health we realise that it is very important to verify if you actually have coeliac disease before commencing treatment for it. A gluten free diet is not always easy to obtain.

If you do have symptoms of CD you may incorrectly self diagnose yourself when it could be another issue such as irritable bowel syndrome (IBS). People with this issue can experience improvements in bloating, abdominal pain, and diarrhoea with a gluten free diet yet still have a different underlying problem. These patients may be misdiagnosed as having celiac disease.

Most important from a diagnosis point of view is that if you actually do have coeliac disease, commencing a gluten free diet before you are diagnosed can lower blood antibody levels and change the appearance of the villi in the small intestine to lose their typical appearance when affected by celiac disease. This will then reduce the efficacy of other predictive methods used to confirm the diagnosis of celiac disease.

The summary of the standard order of diagnosis discussed in more detail below is usually:

Feel ill with several of the symptoms
Get preliminary suspicion of disease by a doctor and undergo stool test
Have blood tests that analyse two or more antibodies related to CD
Have a small bowel biopsy
If CD confirmed, give up all foods containing gluten.
Regain a normal life, sans gluten

STOOL TESTS

Often the first non invasive test that a person suspected of having the disease will undergo is the Stool examination. In Australia a GP or specialist will usually give you a kit where you take your own sample and mail it away to a test centre in a ‘bio hazard' bag.

"Fat in a sample of stool placed on a glass slide can be stained with a dye (Sudan stain) to make the fat visible under the microscope as globules. Stool from patients with celiac disease often contains many stained globules of fat, and Sudan staining is a quick and easy screening test for increased amounts of fat in the stool (steatorrhea). To conclusively diagnose steatorrhea, however, stool is collected over a 72-hour period, and the fat in the stool is chemically measured and quantified. Steatorrheic stools have abnormally high quantities of fat. Since mal-absorption and steatorrhea can occur with other intestinal diseases (such as small intestinal bacteria overgrowth, prior small intestinal resection, extensive Crohn's disease of the small intestine, and chronic pancreatitis), stools with large amounts of fat only raise the suspicion of celiac disease but cannot be used to diagnose celiac disease." Ref 3

BLOOD TESTS

The next step in the Celiac Disease odyssey is usually some form of blood test to test for anti bodies associated with celiac disease. As the medical information is highly technical in matter it is reproduced below without alteration:

"Antibodies are proteins that are produced by the immune system to fight viruses, bacteria, and other organisms that infect the body. Sometimes, however, the body produces antibodies against non-infectious substances in the environment (for example, in hay fever) and even against its own tissues (autoimmunity). Blood tests that are specific for celiac disease include endomysial antibodies, anti-tissue transglutaminase antibodies, and anti-gliadin antibodies. In patients with celiac disease, anti-gliadin antibody is an antibody produced against gliadin in the diet and endomysial and anti-tissue transglutaminase antibodies are antibodies produced against the body's own tissues." Ref 5

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. Ref 2

"Endomysial antibodies and anti-tissue transglutaminase antibodies are highly reliable in diagnosing celiac disease. An individual with abnormally elevated endomysial and anti-tissue transglutaminase antibodies has a greater than 95% chance of having celiac disease. Anti-gliadin antibodies are less reliable and have a high false positive rate. Thus a person with an abnormally elevated anti-gliadin antibody level does not necessarily have celiac disease. Nevertheless, anti-gliadin antibody levels are useful in monitoring the response to treatment because anti-gliadin antibody levels usually begin to fall within several months of successful treatment of celiac disease with a gluten free diet." Ref 5

"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.Ref 5

"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." Ref 5

Antigliadin antibodies

"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." Ref 5

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." Ref 2

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." Ref 2

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." Ref 2

SMALL INTESTINAL BIOPSY

So with all the antibody testing above you may wonder why not stop there. But as you have read, many of the tests are prone to false negatives and false positives, reliant on the skills of the technicians and may be reacting to other auto immune diseases. This is why many specialist prefer the WYSIWYG (what you see is what you get) visual observation of villi in the colon. Again, due to the technical nature of the description this section is also quoted in full:

"Small intestinal biopsy is considered the most accurate test for celiac disease. Small intestinal biopsies can be obtained by performing an esophagogastroduodenoscopy (EGD). During an EGD, the doctor inserts a long, flexible viewing endoscope through the mouth and into the duodenum. A long, flexible biopsy instrument then can be passed through a small channel in the endoscope to obtain samples of the intestinal lining of the duodenum. Multiple samples usually are obtained to increase the accuracy of diagnosis. A pathologist then can examine the biopsies (under a microscope) for loss of villi and other characteristics of celiac disease such as increased numbers of lymphocytes." Ref 5

"Small intestinal biopsy does however, have some limitations. For example, acute viral gastroenteritis and allergy to cow's milk or soy protein can cause abnormal small intestinal biopsies that are indistinguishable from celiac disease. However, acute viral gastroenteritis is not easily confused with celiac disease because of the difference in the acuteness of symptoms. (Acute viral gastroenteritis has a sudden onset of symptoms and last only a few days.) It is however, easier to confuse cow's milk and soy protein allergies with celiac disease, but these allergic conditions are rare and primarily occur in young children. Despite these limitations, small intestinal biopsies are recommended even for individuals who have abnormal antibody tests for celiac disease." Ref 5

What happens after diagnosis and a gluten free diet

In America, "the NIH found that increasing physician awareness of the various manifestations of celiac disease and appropriate use of available testing strategies may lead to earlier diagnosis and better outcomes for celiac patients. They identified six elements essential to treating celiac disease. Ref 4:

C - Consultation with a skilled dietitian,
E - Education about the disease,
L - Lifelong adherence to a gluten-free diet,
I - Identification and treatment of nutritional deficiencies,
A - Access to an advocacy group, and
C - Continuous long-term follow-up.

So while the only treatment for celiac disease is to follow a strict gluten-free diet the relief from the majority of symptoms may occur within the first few days. However it will take at least 3-6 months (sometime up to 2 years) for the intestines to regain their health.

CONCLUSIONS

Unlike other diseases, celiac disease does not have a simple set of obvious symptoms. As its ‘cure' is the removal of gluten from the diet, rather than the addition of drugs, large pharmaceutical companies are unlikely to benefit from improving its diagnosis and treatment. With so many other pressing diseases and few interested in funding research into diet and health or re-engineering the gluten genes it seems like these detection methods may remain the staples for some time yet.

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Article by

Bruce Dwyer - GoLeftfield Marketing

References

Ref 1 http://www.csaceliacs.org/celiac_symptoms.php

Ref 2 http://americanceliac.org/diagnosis.htm

Ref 3 http://www.medicinenet.com/celiac_disease/article.htm

Ref 4 http://www.healthandage.com/public/health-center/15/article/2909/Undiagnosed-Celiac-Disease.html

Ref 5 http://www.webmd.com/digestive-disorders/celiac-disease/celiac-disease-diagnosis-tests