p < 0.05, abatacept vs. placebo. ** p < 0.01, abatacept vs. placebo. *** p < 0.001, abatacept vs. placebo. a Fixed dose approximating 10 mg/ kg (see section 4.2). b Concurrent DMARDs included one or more of the following: methotrexate, chloroquine/ hydroxychloroquine, sulfasalazine, leflunomide, azathioprine, gold, and anakinra. c Major clinical response is defined as achieving an ACR 70 response for a continuous 6-month period. d After 6 months, patients were given the opportunity to enter an open-label study.