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

This test 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.

This test 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 non-gastrointestinal 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 one percent of the U.S. 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 as insulin-dependent diabetes (~6%), thyroiditis (~2-4%) and Sjogren syndrome (~5%). It is also increased in Down syndrome (5-12%), Turner syndrome (~3%), Williams syndrome (3-10%) and selective IgA deficiency (~2-10%).

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 three percent of these individuals develop celiac disease. The risk for developing celiac disease increases when there is a first degree relative with celiac disease (e.g., the risk approaches 40% for siblings with the same HLA genotype as a patient with celiac disease).