|(H & I)|
|Investigation||:||HLA-DQ typing for Coeliac Disease|
|Investigations||HLA-DQ typing for Coeliac Disease||Inform lab before sending||Not required||Specimen type||4ml EDTA||Ideal time to take specimen||Not applicable||Labelling requirements||click here||How to take the specimen||Whole blood into EDTA||Transport to the laboratory||see H&I General Information Page||Test Times||Test is a single assay, no repeat testing requirements are required||Turnround||10 working days||Additional information||In Coeliac disease (CD) certain HLA-DQ antigens are able to present modified gluten peptides to immune cells and initiate the response which leads to CD. Complete testing of both DQ alpha and DQ beta genes is required in order to identify the implicated alleles.
The HLA-DQ molecule is composed of two chains: DQ alpha (encoded by HLA-DQA1 gene) and DQ beta (encoded by HLA-DQB1 gene). The current molecular method allows typing for both the DQB1 and DQA1 chains and this has shown that there are different combinations of HLA-DQ2 and DQ8. Typing of these combinations is important in CD as they carry different risk association.
CD is mediated by T lymphocytes in patients with genetic susceptibility. Most (90%-95%) patients with CD carry HLA-DQ2, while the remainder have HLA-DQ8. Rare exceptions to these associations have been occasionally seen. In 1 study of celiac disease, only 0.7% of patients with celiac disease lacked the HLA alleles mentioned above. It is important to realise that these genes are also present in about 20% of people without CD. Therefore, the mere presence of these genes does not prove the presence of coeliac disease or that genetic susceptibility to celiac disease is present.
There are 2 common combinations of DQ2:
1. DQA1*05:01 with DQB1*02:01 also called DQ2.5 in coeliac literature
2. DQA1*02:01 with DQB1*02:02 also called DQ2.2 in coeliac literature
A single combination of DQ2.5 is enough for presence of coeliac disease.
There are 3 common combinations of DQ8: 1. DQA1*03:01 with DQB1*03:02
2. DQA1*03:02 with DQB1*03:02
3. DQA1*03:03 with DQB1*03:02
Any single combination of DQ8 is associated with coeliac disease.
Disease severity increases when patients carry an additional copy of any of these disease associated combinations
|Additional Examination Requests||A primary sample must be received for this test|