What are the diagnostic criteria for rheumatoid arthritis?
- Morning stiffness lasting >1 hour
- Arthritis of 3 or more joints
- Hand joint arthritis
- Symmetrical joint involvement
- Rheumatoid factor positivity
- Periarticular erosions
- Rheumatoid nodules
A patient is classified as having rheumatoid arthritis if 4 of these 7 criteria are present. The first 4 must be present for >6 weeks.
Assays for anti-CCP antibodies can also be helpful in the diagnosis of RA, though they have not been included to date in the classification criteria. Anti-CCP antibodies are more specific (~90%) for rheumatoid arthritis than RF and they have a similar sensitivity. Their presence also predicts erosive disease.