|Description:||Untreated coeliac disease is characterised by the presence of IgA antibodies to one or more antigens. IgA anti-tissue transglutaminase antibodies are now used as the screening test of choice. All positive samples are then tested for IgA anti-endomysial antibodies.There is a good correlation with disease activity. The widespread use of these tests has led to the realisation that coeliac disease is common in all age groups even the elderly and presentation can be varied. An immune response to tissue transglutaminase or its products is the cause of coeliac disease.
Most untreated coeliacs will have both IgA anti-tTg and endomysial antibodies. IgA anti-tTg tends to appear before anti-endomysial, sometimes before overt symptoms. On a gluten free diet IgA anti-tTg usually disappears after IgA anti-endomysial. Relapse or poor compliance with a gluten free diet is often associated with return of antibody positivity.
Note that coeliac disease is often associated with IgA deficiency. IgA levels are estimated in all patients with suspected coeliac disease. IgA deficient individuals with suspected coeliac disease are tested for IgG anti-tTg and IgG anti-endomysial antibodies. The test for IgA anti-TTg will usually detect IgA deficiency and indicate the need for measurement of IgG antibodies.
Occasionally the standard autoantibody screen will identify anti-reticulin autoantibodies which can suggest coeliac disease. In such cases, the serum will be tested for IgA anti-TTg.
|Indication:||Coeliac disease. Failure to thrive in children, gut disorders, malnutrition, anaemia or osteoporosis in adults.Note that coeliac disease is now diagnosed for the first time in patients of any age.|
|Interpretation:||Samples positive for both IgA anti-TTg and endomysial antibodies are almost certainly from patients with coeliac disease or dermatitis herpetiformis. Samples positive only for IgA anti-TTg may suggest evolving coeliac disease.The commonest cause of ‘false positive’ IgA anti-tTg is a raised total IgA associated with chronic liver disease. Such patients seldom have anti-endomysial antibodies.|
|Sample:||Serum Separator Tube (SST)|
|Assay details:||Various; See anti-tTg and anti-endomysial.|
|Reference range:||See individual tests|
|Assay range notes:||See individual tests|
|Turnaround Time:||3 – 5 days|
|Analysing laboratory:||Immunology The James Cook University Hospital|