Rheumatoid Factor
A positive Rheumatoid Factor does not mean you have rheumatoid arthritis.
Many conditions can lead to a positive Rheumatoid Factor including:
- chronic hepatic and pulmonary diseases
- Rheumatoid Arthritis
- Systemic Lupus Erythematosus
- Systemic Sclerosis (Scleroderma)
- Mixed Connective Tissue Disease
- Sjögren's
- Polymyositis
- Sarcoidosis
- malignancies (especially after therapy)
- AIDS
- mononucleosis
- parasitic infections
- chronic viral infections
- tuberculosis
- subacute bacterial endocarditis
- cryoglobulinemia, etc.
Frequency of positivity of rheumatoid factor in normal individuals also occurs and varies by age from 5% in those younger than 70 to 10-25% in those older than 70. Changes in RF level do not reflect disease activity; however, a high titer does predict increased severity of disease including extra-articular manifestations.
A second or third generation anti-CCP antibody is a more specific test for Rheumatoid Arthritis, but only a good clinician taking a careful history and physical exam can make a correct diagnosis.