Measurement of an antibody detectable in the blood in autoimmune joint diseases. In the diagnosis of rheumatoid arthritis it is interpreted together with the anti-CCP test.
Indication
- Symmetric pain, swelling, and morning stiffness in more than one joint
- Long-standing inflammatory findings in finger and toe joints
- Suspected rheumatoid arthritis (inflammatory joint rheumatism)
- Evaluation of Sjögren's syndrome (with eye and mouth dryness)
- Investigation of cryoglobulinemia
- Differential diagnosis of chronic liver diseases and chronic infections (hepatitis, tuberculosis)
- Monitoring of treatment response and disease activity
Preparation
- No special preparation is required
- Fasting is not mandatory
- Recently experienced infections should be reported to the laboratory
- Any current treatment for rheumatoid arthritis should be communicated to the physician
- The test result must always be interpreted together with anti-CCP and clinical findings
How it's performed
- About 3-5 mL of venous blood is drawn into a gel tube
- The serum is separated
- RF level is measured in IU/mL using the nephelometry or turbidimetry method
- When required, RF subtypes (IgM, IgA, IgG) can be measured separately
- Anti-CCP, CRP, ESR, and complete blood count are recommended in the same session
- The result is reported as a numerical value together with the reference range
Post-procedure
- Results are usually available the same day or within 1 working day
- A positive result alone does not establish the diagnosis of rheumatoid arthritis; it is interpreted together with clinical and imaging findings
- Anti-CCP is more specific and is interpreted together with RF
- Periodic measurements may be made to evaluate treatment response
- Regular follow-up with a rheumatologist is recommended
Risks
- Temporary bruising or tenderness at the blood draw site
- Low-level false positivity in older and otherwise healthy individuals
- Positivity in chronic infections or liver diseases (not specific to a particular disease)
- Very rare vasovagal reaction
FAQ
Does a positive RF mean a diagnosis of rheumatoid arthritis?
No. A positive RF is only a supportive finding. The diagnosis is made together with clinical findings, anti-CCP, imaging, and other tests.
Can RF be positive in healthy people?
Yes. Low-titer positivity may be seen, especially in people over 60, in chronic infections, and in some liver diseases.
What is the difference between RF and anti-CCP?
Anti-CCP is more specific for rheumatoid arthritis and may detect the disease at an earlier stage. RF is more sensitive but less specific; the two are evaluated together.
How long does the result take?
In most laboratories the result is ready the same day, at the latest by the end of one working day.
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