HLA-DRB1 and rheumatoid arthritis: Because of the limited sample sizes in subgroups of interest, our study did not include analyses of interactions of distinct HLA-DRB1 subtypes with GSTM1. Recent findings have shown that different *01 and *04 subtypes appear to contribute equally to SE-smoking interactions in ACPA-positive RA [50], suggesting that analyses of specific SE subtypes may yield limited incremental information.