How is it used?
Coeliac disease tests are primarily used to help diagnose coeliac disease. They are usually ordered on patients with symptoms suggesting coeliac disease, including anaemia and abdominal pain.
Sometimes coeliac testing is ordered to screen for asymptomatic coeliac disease in people who have close relatives with coeliac disease (about 10% of these patients have or will develop coeliac disease) and/or in those who have other autoimmune diseases.
Other tests to help determine the severity of the disease and the extent of a patient’s malnutrition, malabsorption, and the involvement of other organs might include:
Since those with coeliac disease may also experience conditions such as lactose intolerance, coeliac tests may be done in conjunction with other intolerance and allergy testing. Anti-tTG and AGA tests may be ordered at intervals on patients who have been diagnosed with coeliac disease to monitor compliance with a gluten-free diet and to help evaluate the effectiveness of treatment; antibody levels should fall when gluten is removed from the diet.
When is it requested?
Coeliac disease tests are ordered when someone has symptoms suggesting coeliac disease, malnutrition, and/or malabsorption - such as diarrhoea, abdominal pain, weakness, fatigue, weight loss and joint pain. They may be ordered as part of an investigation of anaemia or osteoporosis. In children, coeliac disease tests may be ordered when a child exhibits gastrointestinal symptoms, delayed development, short stature and/or a failure to thrive.
Autoantibody levels should initially be ordered when a patient still has gluten in their diet. Positive or indeterminate results will then be confirmed with a . One or more antibody tests may be ordered when a patient with coeliac 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 relieving symptoms and reversing the intestinal lining damage (this is sometimes still confirmed with a second biopsy).
In children, the use of the ESPGHAN guidelines 2020 is common in Audstralia. If a |TTG result if is greater than 10 times upper limit of normal and a endomyseal antibody is positive, a biopsy may be avoided. These guidelines do not apply to adults. These guidelines also comment on the use of TTG as the most useful test in screening, something which is standard in Australia.
When a patient’s symptoms have not subsided, coeliac disease tests may be ordered to check for dietary compliance and to help the doctor and patient look for either hidden gluten in the patient’s diet or for other reasons for their unrelieved symptoms. Asymptomatic people may be tested if they have a close relative with coeliac disease, but coeliac disease testing is not recommended, at this time, as a screen for the general population.
What does the test result mean?
Some coeliac disease tests and possible results ; ‘+’ indicates presence of antibodies
|Anti-tTG antibodies, IgA
||Anti-tTG antibodies, IgG
||Anti-gliadin antibodies (AGA), IgG
||Probable coeliac disease
||Symptoms not likely due to coeliac disease
||Probable coeliac disease, anti-tTG, IgA due to total IgA deficiency
Positive and indeterminate coeliac disease tests are usually followed by an intestinal . A biopsy is used to make a certain diagnosis of coeliac disease.
If a patient has been diagnosed with coeliac disease and eliminates gluten from his/her 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 the patient may have one of the rare forms of coeliac disease that does not respond to dietary changes. When coeliac disease tests are used to monitor progress, rising levels of autoantibodies indicate some form of noncompliance with a gluten-free diet.
If the person being tested has not consumed any gluten for several weeks prior to testing, then coeliac disease tests may be negative (although this may require many months on a gluten-free diet). If the doctor still suspects coeliac disease, they may do a gluten challenge – have the patient introduce gluten into their diet for several weeks or months to see if the symptoms return. At that time, coeliac tests may be repeated or a biopsy may be done to check for villous atrophy (damage to the villi in the intestine).
Is there anything else I should know?
Although coeliac disease is relatively common, about 0.5% of Australians may be affected, most people who have the disease are not aware of it. This is partly due to the fact that the symptoms are variable - they may be mild or even absent, even when intestinal damage is present on biopsied tissue. Since these symptoms may also be due to a variety of other conditions, a diagnosis of coeliac disease may be missed or delayed - sometimes for years.