Celiac HLA DQ Association With Reflex to Celiac Antibodies tTG IgA, tTG IgG, DGP IgA, DGP IgG, and Total IgA

Whole blood or buccal swabs and serum specimen should be collected to perform reflex assays if criteria is met.

7 mL of blood or four buccal swabs and 3 mL serum

3 mL of blood or four buccal swabs and 1 mL serum

Lavender-top (EDTA) tube or four buccal swabs in a sealed envelope (buccal swab kit) and gel-barrier tube. If submitting buccal swabs, please use kit provided by LabCorp. To obtain the buccal swab kit or to discuss other specimen types, please telephone 800-533-1037.

Aids in the diagnosis of celiac disease and other gluten sensitive enteropathies. The HLA DQ association test provides genotyping for detection of HLA-DQ2 (DQA1*05:01 or 05:05 and DQB1*02:01 or *02:02) and HLA-DQ8 (DQB1*03:02). Patients with DQ2, half DQ2 and/or DQ8 are predisposed to celiac disease. Patients who are positive for any of these celiac-associated alleles are reflexed to testing for antibodies tTG IgA, tTG IgG, DGP IgA, DGP IgG, and Total IgA. A negative result from the HLA DQ Association test essentially rules out celiac disease. In addition to DQ2 and DQ8 status, the report also includes complete DQA and DQB genotypes, homozygosity for DQB1*02, and genetic risk assessment.

The HLA DQ association test detects celiac disease-associated alleles that predispose to the disorder but the test is not diagnostic of celiac disease. More than 95% of celiac disease patients are positive for DQ2, half DQ2, or DQ8, but many individuals with these genetic results do not develop celiac disease.

Celiac antibody testing has high but <100% sensitivity and specificity. Celiac antibody testing is not useful for celiac diagnosis in individuals on a gluten-free diet since these antibodies may no longer be present. Even with appropriate precautions, an occasional specimen may not be satisfactory for testing. In such cases, fresh specimens should be collected for retesting.

HLA DQ association: Polymerase chain reaction (PCR)/sequence-specific oligonucleotide probes (Luminex®). This is a class II antigen level and an allele level test. Celiac antibodies: Enzyme Immunoassay (EIA).

Celiac HLA DQ Association With Reflex to Celiac Antibodies tTG IgA, tTG IgG, DGP IgA, DGP IgG, and Total IgA is useful for individuals with symptoms suggestive of celiac disease and may be considered for asymptomatic relatives of patients with celiac disease to identify silent celiac disease (celiac antibody positivity not currently manifesting symptoms) or genetic predisposition to celiac disease. Early diagnosis of celiac disease and subsequent treatment with a strict gluten-free diet will control disease activity in most cases and can prevent secondary complications of the disorder.

Celiac disease is an autoimmune disorder characterized by a well defined genetic predisposition and sensitivity to gluten (found in wheat, barley and rye) that causes inflammation in the small intestine, villous atrophy, and malabsorption. Celiac disease can present with gastrointestinal symptoms and/or widely variable nongastrointestinal findings such as iron deficiency anemia, dermatitis herpetiformis, osteoporosis, chronic fatigue, short stature, neurologic symptoms, and many more. Gastrointestinal symptoms are present in fewer than 50% of cases of symptomatic celiac disease. Strict avoidance of gluten in the diet will rid inflammation in most cases, and celiac-associated antibodies are likely to disappear with time.

Celiac disease affects approximately 1% of the US population, but only 17% of cases are currently diagnosed. Underdiagnosis is likely due to the variable presentation of celiac disease and clinical overlap with numerous other disorders such as IBS. The prevalence of celiac disease is increased in certain autoimmune disorders such such as insulin-dependent diabetes (~6%), thyroiditis (~2% to 4%) and Sjögren syndrome (~5%). It is also increased in Down syndrome (5% to 12%), Turner syndrome (~3%), Williams syndrome (3-10%) and selective IgA deficiency (~2% to 10%).

Genetic predisposition to celiac disease requires the presence of specific variants of the human leukocyte antigen (HLA) class II genes HLA-DQA1 and HLA-DQB1 to be present. These genes encode the alpha and beta chains of the celiac-associated proteins DQ2 and DQ8. Presence of DQ2, half DQ2 and/or DQ8 is required but not sufficient for the development of celiac disease. One or more of these HLA results are present in 30% of the population but overall, only 3% of these individuals develop celiac disease. The risk for developing celiac disease increases when there is a first degree relative with celiac disease (eg. the risk approaches 40% for sibs with the same HLA genotype as a patient with celiac disease).