Table 1: Criteria for the Classification of Rheumatoid Arthritis

Table 1:
Criteria for the Classification of Rheumatoid Arthritis
Criterion	Definition
Morning stiffness	Morning stiffness in and around the joints, lasting at least 1 hour before maximal improvement.
Arthritis of 3 or more joint areas	At least 3 joint areas simultaneously have had soft tissue swelling or fluid (not bony overgrowth alone) observed by a physician The 14 possible areas are R or L PIP, MCP, wrist, elbow, knee, ankle, and MTP joints.
Arthritis of hand joints	At least one area swollen (as defined above) in a wrist, or in an MCP or PIP joint
Symmetric arthritis	Simultaneous involvement of the same joint areas (as defined in 2) on both sides of the body (bilateral involvement of PIPs, MCPs, or MTPs is acceptable without absolute symmetry)
Rheumatoid nodules	Subcutaneous nodules, over bony prominences, or extensor surfaces, or in juxta-articular regions, observed by a physician
Serum rheumatoid factor	Demonstration of abnormal amounts of serum rheumatoid factor by any method for which the result has been positive in <5% of normal control subjects
Radiographic changes	Radiographic changes typical of rheumatoid arthritis on posteroanterior hand and wrist radiographs, which must include erosions or unequivocal bony decalcification localized in or most marked adjacent to the involved joints (osteoarthritis changes alone do not qualify)
R = Right; L = Left; PIP = Proximal interphalangeal; MCP = Metacarpophalangeal; MTP = Metatarsophalangeal For classification purposes, a patient will be said to have rheumatoid arthritis if he or she has satisfied at least four of these seven criteria. Criteria 1 through 4 must have been present for at least 6 weeks. Patients with two clinical diagnoses are not excluded. Designation as classic, definite, or probable rheumatoid arthritis is not to be made. Adapted from reference 1.

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