October 2015 -- New blood test on the horizon will likely available in two to three years. The tests promise to be highly accurate, even for people who initiated a celiac gluten-free diet without receiving a confirming diagnosis. The test identifies gluten reactive T cells rather than antibodies. Asbjørn Christophersen's work is based upon earlier work by Ludvig M. Sollid's research group and collaboration with Professor Knut E. A. Lundin at the University of Oslo, Faculty of Medicine. A large clinical trial will be completed in 2016.
1. Blood tests for gluten autoantibodies (These are IgA based tests accurate only while on a gluten-containing diet)
2. A small bowel biopsy to assess gut damage. For those with suspected dermatitis herpetiformis, skin biopsies will be taken of the skin near the lesion.
(NOTE: Diagnostic tests should be performed before restricting gluten, to ensure the most accurate diagnosis. The gluten-free diet should be implemented only after the biopsy and discussion with the physician. Follow the gastroenterologist instructions on the length of time and quantity of gluten containing foods to eat prior to the tests.)
The following areas should be considered in the discussion: (The first three are applicable to adults and children. The last is specific to children.)
See What are the Symptoms of Celiac Disease? for a thorough list of possible symptoms.
Depending on the presentation of symptoms, the physician will perform tests to check for some of the following items:
There is no standardization in current tests. A number of tests, sometimes collectively referred to as the Celiac Blood Panel or Cascade, will aid the physician in diagnosis. The tests may include, but are not limited to:
Deamidated gliadin peptide (DGP) antibodies tests developed in 2007 in combination with Tissue transglutaminase (TTG) antibodies and have better accuracy than native gliadin antibodies. Multiplex immunoassay (MIA) measures multiple antibodies simultaneously providing with reduced turnaround time and cost. Combination testing identifies patients who are candidates for an intestinal biopsy. Test panels include AGA to determine if a person's body makes sufficient IgA antibodies for the EMA and TTG results to be reliable. IgA deficiency is, in itself harmless.
Gene tests alone are not used to diagnose celiac disease. Gene tests can only exclude the probability of developing celiac disease. Thirty to forty percent of people in the USA have the genetic predisposition to develop celiac disease. 1% of the population will develop celiac disease. Human leukocyte antigen (HLA) region DQ genes are highly represented in persons diagnosed with celiac disease. Accurate genetic tests for celiac disease require analysis of the configuration of both DQA and DQB genes. Other genes outside of the HLA area have and are being identified. Genetic testing may be useful for family members of a person diagnosed with celiac disease and young children whose immune system is not mature.
May 2011, Digestive Disease Week - Bob Anderson, MD and collaborating researchers presented the first population study results that support the use of a combination of HLA-DQ genetic and serology tests to determine the prevalence of celiac disease. This combination test may ultimately eliminate the standard guidelines of a biopsy. The study also concluded that the cost per diagnosis can be reduced by up to 50%. This non-invasive process would be a cost effective and efficient diagnostic method appropriate for the primary care setting.
How accurate are the tests? Sensitivity/Specificity
In the event that clinical signs and positive laboratory tests indicate probable malabsorption, a biopsy of the small intestine [jejunal] is scheduled to be performed by a gastroenterologist. In this test, a small flexible biopsy instrument is passed through a tube, down the throat, through the stomach and into the upper end of the small intestine where patchy, multiple snippets of tissue are gathered. The tube is removed and the tissue samples are examined under a microscope for signs of damage.
The difference between tissue in a normal small intestine and that found in an undiagnosed or untreated celiac patient is remarkable. The normal finger-like projections (villi), which increase the absorptive surface area of the small intestine, are partially or totally flattened in a person with celiac disease. Enzymes located on the brush border are also drastically reduced. The enzymes produced at the tips of the villi breakdown carbohydrates. Lactase, the enzyme responsible for splitting milk sugar (lactose) so it can be absorbed, is an example of one of these brush border enzymes. This decrease in lactase explains why some untreated celiac patients may not be able to tolerate milk products and will have developed transient or permanent lactose intolerance. At the base of the villi elevated numbers of T-cell lymphocytes (white blood cells) are also present. The small bowel biopsy samples of persons with dermatitis herpetiformis often show similar damage. To view a color-coded illustration of a single villus, visit MEDLINEplus.
1. Lactose tolerance test
2. D-Xylose test
NOTE: At this time there is no standardization in either serological testing or intestinal biopsies.
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