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Test Findings

Elevated Rheumatoid Factor



  • Rheumatoid factor is a heterogeneous group of immunoglobulins against antigens classically found to be present in rheumatoid arthritis.
      • Normal Range

      • <20 U/mL
    • Causes of Elevated Rheumatoid Factor

    • Physiologic - elevated in 15% of normal people
    • Inflammatory disease - rheumatoid arthritis, Sjögren’s, SLE, sarcoidosis, pulmonary fibrosis, cryoglobulinaemia
    • Bacterial infection - subacute bacterial endocarditis, TB, syphilis
    • Viral infection - hepatitis C, EBV, CMV, HIV, rubella
    • Parasitic infection - malaria, toxoplasmosis, Chagas disease
    • Cirrhosis
    • Malignancy
    • Pearls

    • Rheumatoid factor is classically used as a marker of rheumatoid arthritis, with 70% sensitivity and 70% specificity - therefore a positive test does not confirm RA and a negative test does not rule out RA
    • The test is generally interpreted with anti-CCP antibodies as the two tests together are more predictive
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