Allelic distribution and the effect of haplotype combination for HLA type II loci in the celiac disease population of the Valencian community (Spain)

The association between human leukocyte antigen (HLA) class II antigens and celiac disease (CD) was analyzed in a Spanish population. No association with DRB1*04 and DQB1*0302 was noted. The main associated haplotype (70.8%) was DRB1*03-DQB1*0201-DQA1*0501(DR3-DQ2), followed by DRB1*07-DQB1*0202-DQA1*0201 (DR7-DQ2) haplotype, which is associated with DRB1*11-DQB1*0301-DQA1*0505 (DR11-DQ7). The combinations of DR3-DQ2 with DR7-DQ2, and DR7-DQ2 with DR11-DQ7, present a twofold risk compared with each haplotype in homozygosis. An independence test in DR3-DQ2 haplotype found that association with CD was attributable to the whole haplotype, but for DR7-DQ2 was secondary to DQB1/DQA1. There is no need of a double gene dosage to increase the risk. CD-associated alleles typing demonstrates a very high negative predictive value to exclude CD in risk groups.