[Genotyping in patients affected by HLA-related diseases. App development for diagnostic support]

Abstract

HLA typing requests for association studies of immune-mediated diseases are often redundant and inadequate. We designed a series of meta-analyses to evaluate the accuracy of typing and distribution of HLA alleles predisposing to diseases, aiming at developing an app that can help doctors in choosing the most suitable molecular analysis. The first study was on celiac disease (CD) and HLA-DQ in children. We searched all english articles published in the main bibliographic databases up to May 2016. The search strategy has been developed using controlled terms (e.g. MeSH) and free terms. We identified 1885 articles. 1334 abstracts were examined. 46 manuscripts were evaluated, and 13 studies were included in the meta-analysis (740 CD and 943 controls). The risk of developing CD in children with allelic variants encoding the HLA-DQ2.5 and/or HLA-DQ8 molecules has been confirmed. The greatest CD risk resides in carriers of two DQ2.5 molecules, i.e. subjects homozygous for the DQB1*02:01 and DQA1*05 alleles (OR=5.4, 95 % CI=4.1-6.8) compared to any other DQ genotype. Carriers of two DQB1*02:01 (chain β2) alleles and one DQA1*05 (chain α5) allele have the same risk (p=0.8089) of DQ2.5 homozygotes (OR=5.3%, 95 CI=4,1 to 6.5). We found no differences between DQ8/β2 and DQ2.5/DQ8, nor between β2/DQX and DQ2.5/X. We suggest a two-step process: first typing the DQB1*02:01 allele and, in case of a negative result, full typing of HLA-DQ.