Targeting the Immunogenetic Diseases with the Appropriate HLA Molecular Typing: Critical Appraisal on 2666 Patients Typed in One Single Centre.

We compared the immunogenetic data from 2666 patients affected by HLA-related autoimmune diseases with those from 4389 ethnically matched controls (3157 cord blood donors CBD, 1232 adult bone marrow donors BMD), to verify the appropriateness of HLA typing requests received in the past decade. The frequency of HLA-B∗27 phenotype was 10.50\% in 724 ankylosing spondylitis, 16.80\% in 125 uveitis (3.41\% BMD, 4.24\% CBD, P < 0.0001); HLA-B∗51 allele was 15.57\% in 212 Behçet's disease (12.91\% BMD, 9.88\% CBD, P < 0.0001); the HLA-DRB1-rheumatoid arthritis (RA) shared epitope was 13.72\% in 554 RA (10.85\% BMD, 13.48\% CBD, P = 0.016); the carriers of almost one of HLA-DQB1 susceptibility alleles were 84.91\% in 795 celiac disease (CD) and 59.37\% in 256 insulin-dependent diabetes mellitus (IDDM) (46.06\% in 875 CBD, 42.75\% in 662 BMD P < 0.0001). Overall, our results show that the HLA marker frequencies were higher in patients than controls, but lower than expected from the literature data (excluding CD and IDDM) and demonstrate that, in complex immunogenetic conditions, a substantial number of genetic analyses are redundant and inappropriate, burdening to the public health costs. For this reason, we suggest the Italian Scientific Society of Immunogenetics to establish guidelines to improve the appropriateness of typing requests.