Testing

There are several testing options available in order to determine whether you DO have celiac disease, yet we still lack an accurate test that will tell you whether you DON’T have celiac disease. Once ruled in with the condition, you’re in. However, it is nearly impossible to be ruled out.

Currently, if you ask to be tested for celiac disease by one of your doctors, the situation will go something like this: your doctor will order a blood test. If the test is negative, he/she will determine that you do not have celiac disease. If the test is positive, however, they will not determine that you do have celiac disease. Instead, they will refer you to a gastroenterologist for a small bowel biopsy, the ‘gold standard’ of testing. Only then, if the small bowel biopsy is positive will you be diagnosed with celiac disease.

But there are a few problems in these testing methods. Both the common blood panel and small bowel biopsy used for celiac disease diagnosis are fraught with error. Furthermore, other testing options are available such as genetic testing, stool analysis testing and even an over-the-counter blood test not yet available in the United States. Cyrex Labs is another great source for accurate blood antibody testing.

Quit Gluten

Of course, there is an easier way to test whether you are sensitive to gluten. Going on a completely gluten free/casein free diet for at least six weeks.

Casein is the protein found in dairy. It is similar to gluten and has been found to cause an adverse reaction in those who already have villous damage. Therefore, eliminating dairy from your diet for at least the first six weeks may help promote intestinal healing.

So, six weeks on a gluten/casein free diet. Even if your tests are negative for celiac disease, you have the option of trying a gluten free, dairy free diet for at least 6 weeks to determine if your symptoms improve or resolve altogether. This is referred to as a clinical trial. For many people, this is long enough to start to recover from bodily damage caused by gluten consumption. However, there are some people that require a longer period on a gluten free and dairy free or Paleo type lifestyle in order to feel better. Remember, it takes at least 6 months to a year to heal the intestinal lining.

Additional Tests

The Stool Test
Genetic Testing
Sterological Tests
Small Bowel Biopsy

Dr. Kenneth Fine at Enterolab has developed a stool test to measure gluten sensitivity. This test requires collecting a stool specimen from the comfort of your own home and mailing it on to Texas. The specimen is then tested for anti-gliadin IgA and anti-tissue transglutaminase IgA. IgG is not tested, as it is not measureable in the stool.

Dr. Fine argues that the stool analysis is much more accurate than serological tests. In his own research he has found that 64% of patients with microscopic colitis have HLA-DQ2, however very few of them, only 9%, have anti-gliadin antibody in the blood. Dr. Fine argues that small bowel biopsies of these patients show that as many as 70% have mild villous blunting, yet not full villous atrophy. Furthermore, he has found that as many as 76% have anti-gliadin in their stool.

The stool test through enterolab also measures fecal fat, indicating malabsorption. The Gluten Free RN recommends Enterolab’s stool panel combined with the genetic test they offer in order to test for celiac disease/gluten intolerance.

Genetic testing for celiac disease is available at such places as Prometheus Laboratories, Enterolab, and Kimball Genetics.

There are two genes currently associated with celiac disease that these companies are looking for via a blood sample or a cheek swab: HLA DQ2 or HLA DQ8. These tests are extremely accurate and without one of the two genes, you are practically guaranteed not to have celiac disease. These tests can also be helpful in determining your family’s predisposition for the disease. For instance, I am homozygous, meaning I have two of the genes associated with celiac disease. Thus, it is guaranteed that each of my parents has at least one gene and that all of my children will inherit one gene.

There are a few discrepancies with genetic testing. Most tests simply look for the beta subunit of the gene; however a positive alpha subunit could lead to celiac disease and is often missed.

While HLA DQ2 and HLA DQ8 are the genes for celiac disease, their absence does not exclude the possibility of gluten intolerance. New research is beginning to show that only the HLA DQ4 gene has been shown to have no association with gluten intolerance. Yet only 0.4% of the population in the United States contains only this gene. Currently, only Enterolab will tell you whether you have the genes associated with gluten intolerance. However, if 99.6% of the population contains at least one of the genes associated with gluten intolerance and celiac disease, is it necessary?

References

Fine, MD, K. (2003). Early diagnosis of gluten sensitivity: before the villi are gone. Proceedings of the Greater Louisville Celiac Sprue Support Group, https://www.enterolab.com/StaticPages/EarlyDiagnosis.htm

Serological tests can provide an effective first step for celiac disease. These tests typically look for three antibodies that are common in celiac disease:

Anti-tissue transglutaminase (tTG) antibodies
Endomysial antibodies (EMA)
Antigliadin antibodies (AGA)

These antibody tests can be of two classes, the immunoglobulin A (IgA) class or the immunoglobulin G (IgG) test. IgA tests are more sensitive and are more likely to be used. However, individuals with celiac disease are ten times more likely than the average person to be deficient in IgA. Therefore, total IgA and IgG should be tested. In the case of deficiency, IgG must be used.

The antibodies, tTG and EMA are more commonly tested for. AGA is not as sensitive or specific, however it is useful for testing children less than two years of age as tTG and EMA tests are inaccurate in infants.

The problem

Currently, there is not a set standard for ordering this test, and doctors frequently order incomplete panels.
As mentioned, patients with celiac disease are ten times as likely to be IgA deficient then the rest of the population. Unfortunately, this is typically the panel ordered, and when a negative test is found, IgA deficiency is not commonly looked for.
A positive tTG or EMA will not usually result in a diagnosis of celiac disease. Instead most are referred to their gastroenterologist for a small bowel biopsy. Only if the biopsy comes back positive they be diagnosed. However, tTG and EMA elevation directly correlate with gastrointestinal damage due to gluten.
Patients need to be on a gluten containing diet at the time the blood panel is taken. A gluten free diet will lead to a negative test.
With a negative test, patients and doctors often assume that it equals a negative diagnosis of celiac disease for life. This is not the case. These blood tests are highly specific, meaning there is little chance for a false positive. However, they are not extremely sensitive, meaning you need to have full blown celiac disease in order to yield a positive test. A positive blood test means the damage has already been done to your body. Why wait to go on a gluten free diet until this point?

References

Testing for celiac disease. (2009, April). Retrieved from http://digestive.niddk.nih.gov/ddiseases/pubs/celiactesting/index.htm

If a positive serological test results, it is current practice that an intestinal biopsy must be done in order to determine intestinal damage. This “gold standard” for celiac disease diagnosis is considered necessary in the medical world in order to diagnose celiac disease and recommend a gluten free diet. However, many are beginning to recognize this test as no better than “tarnished silver”.

Small bowel biopsies are done during an endoscopy. When the patient is asleep, the doctor passes a long, narrow tube through the patient’s mouth and stomach into their intestine. Small instruments are then passed through the endoscope to remove tissue samples, usually in the descending duodenum. A pathologist can study these tissue samples to look for villi damage.