No single lab test can diagnose rheumatoid arthritis. Instead, rheumatoid arthritis is diagnosed by symptoms and physical signs and by eliminating other diseases that can cause similar symptoms. Physical signs include joint swelling or tenderness. Symptoms that help in diagnosis are stiffness and pain in the same joints on both sides of the body (symmetrical), morning stiffness, and development of rheumatoid nodules.

A medical history and physical examination are usually done to help determine the cause of joint pain. The pattern and nature of joint signs and symptoms are the most important clues to the diagnosis.

Diagnosis is based on a set of classification criteria for rheumatoid arthritis. The following tests may be done to evaluate your symptoms, to rule out other problems, or to monitor treatment.

• Complete blood count (CBC)
• Erythrocyte sedimentation rate (ESR) (may help to assess disease activity)
• C-reactive protein (may help to assess disease activity)
• Rheumatoid factor (RF)
• Antinuclear antibody assay (ANA)
• Anti-CCP (cyclic citrullinated peptide) antibody test (helps confirm diagnosis and may show your risk of having severe symptoms)
• Joint fluid analysis
• Tissue type (human leukocyte antigen) test
• X-rays (see illustrations of X-rays showing rheumatoid arthritis in the feet and rheumatoid arthritis of the hands)

Other tests may be done to check for side effects of treatment. These tests may include:

• Kidney function tests.
• Liver and muscle enzyme tests.
• Bone density test to check for bone loss (osteoporosis).
• Eye examination.

Since rheumatoid arthritis can lead to severe joint destruction and disability over time, regular evaluation by a health professional is important to determine whether current treatment is working or needs to be adjusted.