HLA-DRB1 and rheumatoid arthritis: As RA severity outcomes as well as anti-CPP information were not collected in the framework of the 13th IHWG, we were not able to discuss the relevance of the classification of HLA-DRB1 alleles proposed by Tezenas du Montcel and colleagues [8] regarding RA severity or autoantibody production in the various Caucasoid and non-Caucasoid population samples included in the present study.