Blood Test for Celiac Disease – Positive vs False Negative

Blood Test for Celiac Disease

Celiac disease is a condition in which nutrient absorption is impaired. Gluten, a protein that is commonly found in barley, rye and wheat, causes a negative reaction within the body. When a person with celiac disease ingests foods that contain gluten, his immune system kicks into action. It triggers the destruction of villi that are contained in the lining of the small intestine. Villi are tiny hair like apparatuses that are responsible for the absorption of food nutrients. Over time, the destruction of intestinal villi can lead to malnourishment and illness. The condition is considered both an autoimmune ailment as well as a malapsorption syndrome. Typically, a blood test for celiac disease is used to determine whether or not this action is occurring within the body. However, they are not always entirely accurate, especially in one particular case.

Some people suffer not specifically from celiac disease but from gluten sensitivity. Thus they do not have an autoimmune reaction to gluten, rather they have digestive complaints that may be associated with eating gluten. This particular problem can be tricky because even though a blood test for celiac disease may not show that the condition is present, they symptoms of gluten intolerance such as gas, cramping, bloating, abdominal discomfort and diarrhea may still be present and may appear following foods containing gluten.

The first step in obtaining a celiac disease diagnosis is to link the symptoms to the ingestion of gluten. Because the symptoms of celiac disease in women and men are so similar to other gastrointestinal complaints like irritable bowel syndrome, it is not always easy to pinpoint gluten as the cause. However, once suspected, a blood test for celiac disease is usually indicated. What is looked for during this particular laboratory study is higher than normal concentrations of antibodies. Antibodies are proteins that affect the tissues and the cells of the body. One group of these proteins in particular, anti tissue antibodies called transglutaminase antibodies (tTGA) may be present in higher amounts if celiac disease is present. Additionally, higher than normal concentrations of anti endomysium antibodies may also be present.

Many times, people celiac are easily diagnosed using these types of tests. However, sometimes a person with celiac disease may go undiagnosed if the results come back negative. This can happen for a number of reasons, and often leads to further blood testing. One common reason that the test can come back negative for concentrated antibodies is because the person having the test done started a gluten free diet prior to testing. This is why it is very important that no dietary changes be made prior to having a blood test for celiac disease.

Unfortunately, there is another reason that the most common diagnostic tool for celiac disease may be inadequate, and that is false negatives. New studies point out that these blood tests, which have served as the gold standard of early celiac diagnosis, may be not as sensitive as previously thought. This can mean up to one in ten people may be mistakenly diagnosed as not having celiac disease when they really do. In addition to the sensitivity issues, people with an IgA deficiency (a genetic immunodeficiency) are very susceptible to false negative blood test for celiac disease results. Interestingly enough, people with celiac disease are actually more likely to have an IgA deficiency, making the likelihood of a false negative result in these persons even more probable.

Typically if the indigestion like symptoms of celiac disease including diarrhea and stomach bloating are present, further testing for the condition will be done even if blood work results come back negative. This can include an intestinal biopsy, which is markedly more accurate than a blood based gluten sensitivity test. While it is more accurate and can provide a clear picture of what is going on in the digestive tract, it is invasive and expensive. Thusly, while not perfect, the standard blood test for celiac disease is still the go to first step diagnostic tool.

Once a diagnosis has been confirmed, dietary changes are the only means to combat the symptoms of the condition. In most cases (with the exception of refractory celiac disease where diet does not help) dietary changes quickly lead to a reduction in uncomfortable symptoms. Working with a health care provider to either confirm or eliminate a potential celiac diagnosis may be a long and difficult journey. However, the symptom relief that can come from making the appropriate dietary changes is often worth the effort.

References:
http://digestive.niddk.nih.gov/ddiseases/pubs/celiac/#diagnosis

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