Avoid ordering these autoantibodies in patients with arthralgia (joint pain) but who do not meet the CSA criteria or have arthritis (>one swollen joint) on physical exam. EULAR defines CSA at risk for developing Rheumatoid Arthritis (RA) as having 3 or more parameters including new joint symptoms <1 year, symptoms located in metacarpophalangeal (MCP) joints, morning stiffness >60 min, most severe symptoms in the morning, 1st degree relative with RA, and difficulty making a fist and positive MCP squeeze test on physical exam. Even in CSA with positive RF and ACPA, more than 30%-60% of patients will not develop RA over the next two years. Most musculoskeletal pain causing global disability is not related to rheumatoid arthritis. Inappropriate testing of RF serology in patients with low likelihood of RA is associated with low positive predictive value (PPV) and increased cost.
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