The study will consist of a screening visit followed by a washout period for all disease modifying antirheumatic drugs (DMARDs) and anti-cytokine therapies except MTX. The washout period will be 4 weeks for sulfasalazine, hydroxychloroquine, azathioprine, D-penicillamine, etanercept, and anakinra, 8 weeks for gold, infliximab, and adalimumab, and 12 weeks for abatacept.