Assessment of the DQ Heterodimer Test in the Diagnosis of Celiac Disease in the Canary Islands (Spain)

Abstract

BACKGROUND: Celiac disease is a multifactorial disorder of the proximal small intestine associated with a permanent intolerance to gluten. The HLA-DQ(alpha1*0501, beta1*02) heterodimer is strongly associated with this disease. MATERIALS AND METHODS: The authors studied a sample of 354 unrelated Caucasoid individuals: 118 patients with celiac disease and 236 control subjects. All patients and controls subjects were born in Gran Canaria (Canary Islands) at least two generations ago. The authors typed the HLA-DQA1 and DQB1 genes by DNA methods. The positive and negative predictive values of the test were studied. RESULTS: The mean age at diagnosis was 25.4 months, with a statistically significant proportion of females (64.4%, P < 0.002). For DQB1 gene, the susceptibility allele found was DQB1*02 (relative risk [RR] = 7.60, confidence interval [CI]: 5.35-10.78), whereas for the DQA1 gene, the susceptibility alleles found were DQA1*0501 (RR = 2.99, CI: 2.16-4.14) and DQA1*0201 (RR = 1.88, CI: 1.25-2.82). The presence of the DQ(alpha1*0501, beta1*02) heterodimer was strongly associated with the disease (92.4% in the patients group vs. 21.6% in control subjects). HLA-DQ8 heterodimer was absent in the authors' patients. DQB1*02 homozygous subjects presented a higher relative risk for celiac disease. There was no correlation of DQB1*02 dosage with age at onset below 12 years of age or with gender distribution. Sensitivity, specificity, and the positive and negative predictive values of the test were 92.4%, 78.4%, 68.1%, and 95.4%, respectively. CONCLUSIONS: The presence of the DQ2 (DQA1*0501/DQB1*02) heterodimer is strongly associated with celiac disease in the population studied by the authors. The value of this test derives from its ability to exclude disease when a negative result occurs.