Coeliac disease (CD)
Our new pathway reduces the risk of missing IgA-deficient patients.
Coeliac disease (CD) is an immune-mediated disease of the intestines that is triggered by the ingestion of gluten in genetically susceptible individuals. Gluten is the major protein component
of wheat, rye, and barley. Genetic predisposition does play a key role in CD, and it is well known that CD is strongly associated with specific HLA class II genes known as HLA-DQ2 and HLA-DQ8. Approximately 95% of CD patients express HLA-DQ2, and the remaining patients are usually HLA-DQ8 positive. The negative predictive value for both tests is higher than 99%. However, the HLA-DQ2 allele is common and is carried by approximately 30% of Caucasian individuals. Thus, HLA-DQ2 or HLA-DQ8 is necessary for disease development but is not sufficient for disease development; its estimated risk effect is only 36-53%.
Note: History taking is important if a patient has been on a gluten-free diet for 6-12 months, approximately 80% will lose their antibody response. After 5 years this increases to >90%.
Coeliac pathway
Tissue Transglutaminase IgA (TAA) as a single test. This can be requested as a single test as well as being included as one of the tests in the Coeliac/Coaelic Sensitivity Profile (GSA).
- Initial TTG IgA samples are received and tested
- If TTG IgA is LOW <0.2 U/ml reflex testing for Total IgA will be undertaken
- If Total IgA is LOW <0.1 g/L then reflex testing for Gliadin IgG test will be undertaken
- If TTG IgA is HIGH (>/= 10 U/ml) or in the equivocal range (7–10 U/ml) then reflex testing for Endomysial IgA will be undertaken as a confirmatory test for first time positive samples.
Endomysial IgA (AEAB) as a single test. This can be requested as a single test as well as being included as one of the tests in the Coeliac/Coaelic Sensitivity Profile (GSA).
- If TTG IgA is positive endomysial IgA will be carried out as a confirmatory test. This only needs to be done once in the patients history.
Deamidated Gliadin IgG (AGAB) as a single test. This can be requested as a single test as
well as being included as one of the tests in the Coeliac/Coaelic Sensitivity Profile (GSA). This may be useful when testing children’s samples. Appropriate clinical comments will be added to results – see table below.
|
TTG IgA result U/ml |
Total IgA result |
Deamidated gliadin |
Comment |
|---|---|---|---|
|
0.2 to 10 |
N/A |
N/A |
Coeliac disease unlikely (please note that if the patient has no dietary gluten results may appear false negative) |
|
>/= 10 |
N/A |
N/A |
Suggestive of coeliac disease |
|
<0.2 |
>/= 0.1 |
N/A |
Coeliac disease unlikely (please note that if the patient has no dietary gluten, results may appear false negative) |
|
<0.2 |
<0.1 |
>/=10 |
Consistent with coeliac disease in a patient with selective IgA deficiency |
|
<0.2 |
<0.1 |
< 7 |
Coeliac disease unlikely (please note that if the patient has no dietary gluten, results may appear false negative) |
|
<0.2 |
<0.1 |
7-10 |
Result equivocal suggest referral to a gastroenterologist for consideration of duodenal biopsy |