Diagnosis of RA
The American College of Rheumatology established criteria for the diagnosis of rheumatoid arthritis. To diagnose the disease, symmetrical arthritis in at least 3 joint areas and morning stiffness must be present for longer than 6 weeks. Physical findings that are used to help diagnose RA include rheumatoid nodules and warmth and synovial soft tissue swelling in affected joints.
Rheumatoid arthritis is diagnosed based on the patient's medical history, a physical examination, laboratory tests, and imaging tests (e.g., x-rays). Diagnosis also involves ruling out other types of arthritis (e.g., osteoarthritis) and conditions, such as viruses (e.g., hepatitis B and C), sarcoidosis, Lyme disease, and rheumatic fever.
A medical history includes information about the type, location, and severity of symptoms. During the physical examination, the physician looks for joint swelling, tenderness, and loss of joint function.
- Anti-CCP antibodies (this is one of the most specific laboratory tests to help diagnose RA)
- Complete blood count (CBC; used to measure levels of red blood cells, white blood cells, and platelets)
- C-reactive protein (CRP; used to detect inflammation)
- Erythrocyte sedimentation rate (ESR; used to detect inflammation)
- Rheumatoid factor (latex agglutination test; used to detect levels of this antibody, which are elevated in most patients who have RA)
Imaging tests (e.g., x-rays) are used to help diagnose rheumatoid arthritis and to monitor progression of the disease. X-rays can detect swelling in surrounding tissue and loss of bone density in affected joints.
Other imaging tests that may be used include magnetic resonance imaging (MRI) and ultrasound, which can detect inflammation earlier than standard x-rays. Bone densitometry (DEXA), which is used to detect osteoporosis, may be an important diagnostic tool in patients who have rheumatoid arthritis.