Deamidated gliadin peptide (DGP) antibodies (anti-DGP), IgA or IgG — may be used in some people with suspected celiac disease who are negative for anti-tTG, especially children younger than 2 years old. DGP IgG testing along with anti-tTG IgG is recommended by the American College of Gastroenterology for people who have low IgA or IgA deficiency. If the anti-DGP test is positive, it may be used to monitor celiac disease.
Celiac disease is a gluten enteropathy occurring in both children and adults. The disease is probably underdiagnosed in that it may affect as much as 1% of the population in the United States. The condition is characterized by a sensitivity to gluten (found in wheat, barley, and rye) that causes inflammation and atrophy of the villi of the small intestine, malabsorption, etc. This sensitivity to gluten may also be seen in dermatitis herpetiformis. Strict avoidance of gluten in the diet will control disease activity, and antibodies to serum markers will disappear with time.
To confirm a diagnosis of celiac disease, a biopsy of the small intestine is examined to detect damage to the intestinal villi. However, given the invasive nature and cost of a biopsy, antibody tests are often used to identify those individuals with high probability of having celiac disease.
Celiac disease tests are ordered when someone has signs and symptoms suggesting celiac disease, malnutrition, and/or malabsorption. The symptoms are often nonspecific and variable, making the disease difficult to spot. The symptoms may, for a time, be mild and go unnoticed and then progressively worsen or occur sporadically. The condition can affect different parts of the body.
Digestive signs and symptoms may include:
- Abdominal pain and distension
- Bloody stool
- Chronic diarrhea or constipation
- Greasy, foul-smelling stools
Other signs and symptoms may include:
- Iron-deficiency anemia that does not respond to iron supplements
- Easy bruising and/or bleeding
- Bone and joint pain
- Defects in dental enamel
- Fatigue, weakness
- Mouth ulcers
- Weight loss
- In adults, infertility, osteoporosis
In children, celiac disease tests may be ordered when a child exhibits:
- Digestive tract symptoms
- Delayed development
- Short stature
- Failure to thrive
Many people with celiac disease have dermatitis herpetiformis, a disease that causes itchy blisters on the skin. There is also an increased risk for developing intestinal lymphoma, a form of cancer.
One or more antibody tests may be ordered when someone with celiac disease has been on a gluten-free diet for a period of time. This is done to verify that antibody levels have decreased and to verify that the diet has been effective in reversing the intestinal lining damage (this is sometimes still confirmed with a second biopsy).
Asymptomatic people may be tested if they have a close relative such as a parent or sibling with celiac disease, but celiac disease testing is not recommended at this time as a screen for the general population.
|TTG, IGA||TOTAL IGA||TTG, IGG||Deamidated gliadin peptide (DGP) antibodies, IGA||Deamidated gliadin peptide (DGP) antibodies, IGG||DIAGNOSIS|
|Positive||Normal||Not performed||Not performed||Not performed||Presumptive celiac disease|
|Negative||Normal||Negative||Negative||Negative||Symptoms not likely due to celiac disease|
|Negative||Low||Positive||Negative||Positive||Possible celiac disease (false negative anti-tTG, IgA and anti-DGP, IgA are due to total IgA deficiency)|
|Negative||Normal||Negative||Positive||Positive (or not performed)||Possible celiac disease (may be seen in children less than 3 years old)|
All positive and indeterminate celiac disease tests are typically followed by an intestinal biopsy. A biopsy is used to make a definitive diagnosis of celiac disease.
If you have been diagnosed with celiac disease and you eliminate gluten from your diet, then the autoantibody levels should fall. If they do not fall and the symptoms do not diminish, then there may either be hidden forms of gluten in the diet that have not been eliminated (gluten is often found in unexpected places, from salad dressings to cough syrup to the adhesive used on envelopes) or you may have one of the rare forms of celiac disease that does not respond to dietary changes.
If you have not consumed any gluten for several weeks to months prior to testing, then celiac disease tests may be negative. If your healthcare practitioner still suspects celiac disease, the practitioner may do a gluten challenge – have you introduce gluten back into your diet for several weeks or months to see if your symptoms return. At that time, celiac disease tests may be repeated or a biopsy may be done to check for damage to the villi in the intestine.
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