Four of seven criteria are required to classify a patient as having rheumatoid arthritis. Criteria 1-4 must be present for at least 6 weeks.
1. Morning stiffness lasting 1 hr.
2. Arthritis of three or more joint areas: Simultaneous soft tissue swelling or joint effusions of at least three joint areas. The 14 possible joint areas involved are right or left proximal interphalangeal, metacarpophalangeal, wrist, elbow, knee, ankle & metatarsophalangeal joints.
3. Arthritis of hand joints: Arthritis of wrist, metacarpophalangeal joint, or proximal interphalangeal joint.
4. Symmetric arthritis: Simultaneous involvement of the same joint areas on both sides of the body.
5. Rheumatoid nodules: Subcutaneous nodules over bony prominences, extensor surfaces, or juxta-articular regions.
6. Serum rheumatoid factor: Demonstration of abnormal amounts of serum rheumatoid factor.
7. Radiologic changes: Typical changes of RA on postero-anterior hand & wrist radiographs that must include erosions or unequivocal bony decalcification localized in or most marked adjacent to the involved joints.