ACR/EULAR (American College of Rheumatology, EULAR = European League Against Rheumatism) classification criteria for rheumatoid arthritis (RA).
| Stage | Description | Score |
| A | Joint involvement (synovitis/inflammation of the synovial membrane) | |
| 1 large joint1 | 0 | |
| 2-10 large joints | 1 | |
| 1-3 small joints2 (with/without involvement of large joints). | 2 | |
| 4-10 Small joints (with/without involvement of large joints). | 3 | |
| > 10 joints (including at least 1 small joint) | 4 | |
| B | Serology (at least 1 test result required). | |
| Negative rheumatoid factors (RF) and negative CCP-AK. | 0 | |
| Low-positive RF or low-positive CCP-AK. | 2 | |
| High-positive RF or high-positive CCP-AK. | 3 | |
| C | Acute phase reaction (at least 1 test result required). | |
| Inconspicuous CRP and ESR (erythrocyte sedimentation rate). | 0 | |
| Elevated CRP or accelerated ESR (erythrocyte sedimentation rate). | 1 | |
| D | Duration of complaints | |
| <6 weeks | 0 | |
| ≥ 6 weeks | 1 |
1Large joints: shoulder, elbow, hip joint, knee, ankle 2Small joints:
- Wrist joints,
- Metacarpophalangeal joints [MCP; connect the metacarpal bones (ossa metacarpi) to the proximal phalanges of the fingers (digiti)],
- Proximal interphalangeal joints [PIP; joint between the proximal phalanx (proximal phalanx) and the medial phalanx (middle phalanx)],
- Metatarsophalangeal joints [basic joints between metatarsal bones (Os metatarsale) and proximal phalanges (Phalanges proximales)].
Assessment: ≥ 6 out of 10 points are required for “definite RA”.
Staging of rheumatoid arthritis according to disease progression.
| Stage | Description |
| I | Minor swelling, episodic, morning stiffness, general signs of illness |
| II | Constant synovitis (inflammation of the inner layer of the joint capsule), progressive decrease in joint mobility, involvement of connective tissue such as capsules, tendons, bursa, no joint deformities yet |
| III | Joint deformities, muscle atrophies (muscle atrophy), appearance of rheumatoid nodules, onset of joint instability |
| IV | Pronounced joint deformities, joint instability, ankyloses (stiffening of joints with complete loss of motion) |
Assessment of disease activity using the disease activity score (DAS28).
The DAS28 is used to record the disease activity of 28 joints. It integrates:
- Pressure-painful joints (0-28; each measured at 28 EULAR-defined joints).
- Swollen joints (0-28)
- Inflammatory parameters (ESR (mm/h) or CRP).
- Patient assessment of disease activity (0-100 mm visual analog scale (VAS)).
The DAS28 is calculated using the following formula:
After completion of the examination, the result obtained with this formula is described by a score between 0 and 10:
Interpretation
- DAS28 < 2.6: clinical remission.
- DAS28 ≥ 2.6 to < 3.2 low disease activity.
- DAS28 between 3.2 and < 5.1: moderate disease activity
- DAS28 ≥ 5.1: high disease activity.