How is Rheumatoid Arthritis Diagnosed?

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There is no single test to diagnose rheumatoid arthritis. The diagnosis is made from a combination of clinical symptoms and findings, supported by various blood tests such as rheumatoid factor, anti-CCP antibodies and elevated inflammatory markers. However, up to 30% of patients have completely normal blood tests.

Rheumatoid factor is a group of non-specific antibodies that can occur in healthy individuals who will never get rheumatoid arthritis. It can be elevated in many diseases such as hepatitis, chronic infection or other inflammatory diseases. It does not cause rheumatoid arthritis. The level can fluctuate during the course of disease but it does not correlate with disease activity and it does not normalise with treatment. If you have rheumatoid arthritis, it is not necessary to monitor the level regularly.
Anti-CCP antibodies are much more specific for rheumatoid arthritis, and the disease tends to be more destructive if you have this antibody. Similar to rheumatoid factor, the level does not fall or normalise with treatment, and hence it is not necessary to monitor the level regularly.

Inflammatory markers such as ESR and CRP are often elevated during active disease and can be good markers to monitor treatment response. The higher the level, the more active the disease is. However, both are also elevated during acute infection and care must be taken to interpret an elevated reading.

In some patients the blood tests can be normal and the clinical features are subtle. Your rheumatologist may consider further investigations to look for active joint inflammation, such as MRI or a Power Doppler ultrasound study to confirm the presence of active inflammation or erosion.

Joint X-rays are normal in early disease and normal X-rays do not exclude rheumatoid arthritis.