Rheumatoid Factor (RF)

The Rheumatoid Factor (RF) test measures the level of RF antibodies in the blood. RF is an autoantibody that can target the body’s own tissues, and its presence is often associated with autoimmune diseases, particularly rheumatoid arthritis (RA). While RF is a key marker for RA, it may also be elevated in other conditions or even in healthy individuals.

1. What Is Rheumatoid Factor?

• RF is an antibody produced by the immune system that mistakenly targets the body’s own immunoglobulin G (IgG) antibodies.

• It is most commonly associated with autoimmune diseases such as rheumatoid arthritis and Sjögren's syndrome.

• The RF test measures the quantity of this antibody in the blood.

2. Why Is the RF Test Performed?

This test is used to:

• Help diagnose rheumatoid arthritis, especially in individuals with joint pain and inflammation.

• Support the diagnosis of other autoimmune diseases, such as Sjögren’s syndrome or mixed connective tissue disease.

• Monitor disease activity or treatment response in patients with RA.

3. RF Reference Range

• Normal: < 14 IU/mL (international units per milliliter)

• Values above the reference range are considered positive.

• Reference ranges may vary slightly between laboratories.

4. Interpreting RF Results

🔹 Positive RF:

• May support a diagnosis of rheumatoid arthritis, especially if symptoms are present.

• May also occur in other conditions: Sjögren’s syndrome, lupus, chronic infections (e.g., hepatitis, tuberculosis), or even in healthy older adults.

• Higher RF levels are more strongly associated with RA severity.

🔹 Negative RF:

• Does not rule out RA (seronegative RA is possible).

• May indicate a different form of arthritis or musculoskeletal condition.

5. What Can Affect RF Levels?

• Age (mild elevations are more common in elderly individuals)

• Chronic infections or liver disease

• Other autoimmune or inflammatory conditions

• Certain medications or recent vaccinations (rare)

6. How Is the Test Performed?

• A blood sample is drawn from a vein.

• No fasting or special preparation is typically required.

7. When to See a Doctor

🚨 Contact your healthcare provider if you:

• Experience persistent joint pain, stiffness, swelling, or fatigue.

• Have a positive RF test and need further evaluation for autoimmune disease.

• Are being monitored for known rheumatoid arthritis or similar conditions.

🔹 Key Takeaways

✅ RF is a common marker used in diagnosing rheumatoid arthritis and related autoimmune diseases.

✅ A positive result supports, but does not confirm, an autoimmune diagnosis.

✅ RF results must be interpreted in combination with symptoms, other lab tests (e.g., anti-CCP), and clinical findings.