The diagnosis of Rheumatoid Arthritis (RA) has historically relied on a set of specific criteria to ensure consistent classification and study of the disease. The "7 diagnostic criteria" most commonly refer to the 1987 criteria established by the American Rheumatism Association (ARA), now known as the American College of Rheumatology (ACR). Meeting a certain number of these criteria helps clinicians classify a patient as having RA.
These criteria focus on various clinical and laboratory findings that are characteristic of rheumatoid arthritis:
| Criterion | Description |
|---|---|
| 1. Morning Stiffness | Patients experience stiffness in and around the joints lasting for at least one hour before maximal improvement. This stiffness is typically worse in the morning. |
| 2. Arthritis of 3 or More Joint Areas | A physician observes soft tissue swelling (arthritis) in three or more joint areas simultaneously. These areas can include the proximal interphalangeal (PIP), metacarpophalangeal (MCP), wrist, elbow, knee, ankle, and metatarsophalangeal (MTP) joints. |
| 3. Arthritis of Hand Joints | There is observed swelling (arthritis) of at least one of the following joint areas: the proximal interphalangeal (PIP) joints, metacarpophalangeal (MCP) joints, or wrist joints. These hand and wrist joints are very commonly affected in RA. |
| 4. Symmetric Arthritis | The involvement of joint areas occurs symmetrically, meaning the same joint areas on both sides of the body are simultaneously affected. For example, swelling in both left and right wrist joints. Bilateral involvement of PIP, MCP, or MTP joints without absolute symmetry is also acceptable. |
| 5. Rheumatoid Nodules | The presence of subcutaneous nodules observed by a physician. These nodules are typically firm lumps found over bony prominences, extensor surfaces (like elbows), or in juxta-articular areas (near joints). |
| 6. Serum Rheumatoid Factor | The detection of abnormal amounts of serum rheumatoid factor (RF) in the blood. This is determined by a method for which the laboratory's normal range has been established, or the test is positive for a method that is positive in less than 5% of normal control subjects. RF is an autoantibody found in a significant percentage of RA patients. |
| 7. Radiographic Changes | Evidence of erosions or unequivocal bony decalcification localized in or most marked adjacent to the involved joints, as viewed on posteroanterior hand and and wrist X-rays. It's important to note that degenerative changes alone (e.g., from osteoarthritis) do not qualify. |
For classification purposes using these criteria, a patient is generally considered to have rheumatoid arthritis if they have satisfied at least four of these seven criteria. Importantly, the first four criteria (morning stiffness, arthritis of 3+ joint areas, arthritis of hand joints, and symmetric arthritis) must have been present for at least six weeks.
