To rule out rheumatoid arthritis, most important among the followings is?
DR4 is strongly associated with RA(also with Type 1 DM Pemphigus vulgaris).

Other options

HLA-B27 is associated with seronegative spondyloarthropathies (ankylosing spondylitis, Psoriatic arthritis, Reiter’s syndrome, reactive arthritis) and acute anterior uveitis
HLA DR8 is associated with Type 1 DM.
HLA DQ1 is associated with pemphigus vulgaris.
HLA DR8
HLA DQ1
HLA B27
HLA DR4