If confirmed, these findings would support the use of HLA-DRB1 genotyping, along with CCP2 concentration monitoring, as a precision medicine tool to guide treatment of RA via T-cell co-stimulatory blockade, and as a predictor of abatacept efficacy in patients with early autoantibody-positive RA. This evidence concerns the gene HLA-DRB1 and rheumatoid arthritis.