Rheumatoid Factor (RF) is an antibody that can be detected in the blood and is most commonly associated with autoimmune diseases, particularly rheumatoid arthritis (RA). RF is produced when the immune system mistakenly targets the body’s tissues, specifically attacking the synovium, which lines the joints.
RF is an important marker in diagnosing and managing rheumatoid arthritis and other autoimmune conditions. However, it can also be found in healthy individuals and other diseases.
Elevated Rheumatoid Factor
As suggested by the name, a high level of circulating RF is often related to rheumatoid arthritis. However, RF is not considered a specific biomarker for RA, meaning it may also be present in other conditions. It may indicate other collagen vascular diseases such as SLE, scleroderma, or Sjogren's syndrome. It is also elevated in conditions such as leprosy, tuberculosis, hepatitis, syphilis, malignancy, and thyroid disease, and in a significant percentage of otherwise normal elderly patients.
The higher your RF test result, the more likely you have a condition linked to rheumatoid factor. An RF antibody value greater than three times the upper limit of normal is considered a high positive. However, a positive RF alone cannot diagnose any condition.
Potential Factors Affecting RF Test Results
- Viral and parasitic infections
- Preexisting chronic medical conditions
- Vaccinations
- Older age
- Smoking
Normal or Low RF Levels
- Seronegative rheumatoid arthritis: Some patients with RA may test negative for RF, known as seronegative RA.
- Healthy individuals: RF can sometimes be present in healthy individuals, particularly older adults, without any associated disease.
- Normal or low result with symptoms: Some patients with rheumatoid arthritis or other autoimmune conditions may have normal or low RF levels, yet still experience symptoms typical of these diseases.
- Negative result: This is good, but doesn't completely rule out RA.
Elevated Rheumatoid Factor - Symptoms
- Joint symptoms: Pain, stiffness, swelling, and tenderness, particularly in the small joints of the hands and feet.
- Systemic symptoms: Fatigue, low-grade fever, weight loss, loss of appetite, and malaise.
- Rheumatoid nodules: Firm lumps under the skin, particularly around pressure points like the elbows.
- Other: Dry eyes, dry mouth, and inflammation in organs such as the lungs, heart, and blood vessels.
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