What are the other Names for this Test? (Equivalent Terms)
- AGA (Anti-Gliadin Antibodies) Test
- Anti-Reticulin Antibodies (ARA) Test
- tTGA Test
What is Celiac Disease Test? (Background Information)
- Celiac disease is a disorder caused by inappropriate response of the immune system to dietary gluten. Gluten is a protein present in wheat; similar proteins occur in barley and rye
- Tests for celiac disease help in diagnosing, monitoring, and assessing the severity of this condition
- The gold standard test to diagnose celiac disease is performing an intestinal biopsy, where tissue from the intestine is removed by invasive means and examined under a microscope, by a pathologist for changes suggestive of celiac disease
- Considering the invasive nature and cost of the procedure, blood tests are now performed to identify individuals with possible celiac disease. Individuals, who test positive for the disorder on blood examination, may then be subjected to biopsy procedures
- The blood tests for celiac disease are all aimed at detecting certain antibodies. These are proteins produced by the immune system in response to any perceived threat to the body. Two classes of antibodies are tested:
- IgA - most important, present in intestinal secretions
- IgG - mainly helps in individuals, who suffer from IgA deficiency
Celiac Disease Tests (antibody tests) that may be conducted include:
- Anti-tissue Transglutaminase Antibody (anti-tTG) Test:
- The IgA antibody against enzyme transglutaminase is tested
- The American College of Gastroenterology (ACG) prefers that this test be performed in individuals over 2 years of age, to detect celiac disease
- In IgA deficient individuals, IgG class ‘anti-tTG’ may be tested. To find out whether an individual is IgA deficient or not, quantitative IgA test (total IgA) may be performed alongside
- Deaminated Gliadin Peptide (DGP) Antibodies Test:
- This test may be performed in children under 2 years of age
- It may be positive in celiac disease patients, who test negative for anti- tTG
- IgA levels are assessed; IgG levels may be examined in IgA deficient individuals
- Anti-Gliadin Antibodies (AGA) Test: This less commonly used antibody test, looks for IgA and IgG antibodies against gliadin, a component of gluten
- Anti-Endomysial Antibodies (EMA) Test:
- EMAs are IgA antibodies, detectable in the presence of intestinal lining damage
- Individuals suffering from other immune disorders, dermatitis herpetiformis, may also produce this antibody
- Anti-Reticulin Antibodies (ARA) and Anti-Actin (F-Actin) Ig A class antibodies: The F-Actin antibody is an indicator of increased intestinal damage
What are the Clinical Indications for performing the Celiac Disease Test?
Indications for Celiac Disease Antibody Testing include:
- To detect celiac disease in individuals with suggestive symptoms, such as:
- Abdominal pain
- Diarrhea, greasy stools
- Bone or joint pain
- Weight loss and pallor
- Children with celiac disease show growth that is below the mean expected for their age
- In an individual with known celiac disease, to check effectiveness of gluten-free diet in lowering antibodies
- To screen asymptomatic individuals having a history of celiac disease in close relatives
How is the Specimen Collected for Celiac Disease Test?
Sample required: Blood
Process: Blood sample is drawn through a needle inserted into the vein (arm).
Preparation required: While testing for celiac disease, it is necessary to consume foods containing gluten, for several weeks prior to sample collection. This is done to ensure that antibodies are present, during the time of testing. No such diet adherence is required, when testing is performed for monitoring the condition.
What is the Significance of the Celiac Disease Test Result?
The possible test outcomes and their interpretations are as follows:
- Positive IgA Anti-tissue Transglutaminase Antibody (anti-tTG) with normal total Ig A: This most likely indicates the presence of celiac disease. An intestinal biopsy is required to make a definitive diagnosis
- Negative Anti-tissue Transglutaminase Antibody (anti-tTG, IgA and IgG), Deaminated Gliadin Peptide (DGP) Antibodies, and Anti-Gliadin Antibodies (AGA): Such an outcome rules out the presence of celiac disease
- Negative IgA Anti-tissue Transglutaminase Antibody (anti-tTG) with positive IgG anti-tTG and Anti-Gliadin Antibodies (AGA) in the setting of a low total IgA: Possible case of celiac disease with IgA deficiency
- Negative IgA and IgG Anti-tissue Transglutaminase Antibody (anti-tTG) with positive IgA Deaminated Gliadin Peptide (DGP) Antibodies in the setting of normal total IgA: Observed in children (below 3 years of age) with possible celiac disease
- In an individual with known celiac disease, a positive F-actin antibody test indicates severe intestinal damage
- During monitoring, the individual is started on a gluten-free diet and antibody tests are performed, to check for a decreasing trend. If antibodies do not decrease, it indicates a lack of compliance with dietary changes, or the presence of hidden gluten in diet. Very rarely, it may indicate the presence of a form of celiac disease that is resistant to dietary modification
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
Other tests that may be performed to assess an individual with celiac disease include:
- Complete blood count and tests for iron, iron binding capacity, and ferritin - to evaluate possible anemia
- Comprehensive metabolic panel
- Tests to check for inflammation - erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
- Stool fat
- Vitamins D, B12, and folate
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.