Rheumatoid Factor (RF)
Rheumatoid factor (RF) is an autoantibody that attacks healthy tissue, particularly in the joints. It is most commonly used to help diagnose rheumatoid arthritis.
Category: Inflammation & Immune
Also known as: rheumatoid factor, rf, ra factor, rheumatoid factor quantitative, reumatoidni faktor
Reference range: 0–14 IU/mL (Source: ABIM)
Standard unit: IU/mL
High values may indicate
High rheumatoid factor levels may indicate rheumatoid arthritis, Sjogren's syndrome, systemic lupus erythematosus, chronic infections (hepatitis C, tuberculosis), or other autoimmune disorders.
Low values may indicate
Low or negative rheumatoid factor levels are normal. However, some people with rheumatoid arthritis may have negative RF (seronegative RA).
Frequently asked questions
- What is a normal Rheumatoid Factor (RF) level?
- A typical reference range for Rheumatoid Factor (RF) is 0–14 IU/mL (source: ABIM). Reference ranges vary by laboratory, age, and sex, so always compare against the range on your own lab report.
- What units is Rheumatoid Factor (RF) measured in?
- Rheumatoid Factor (RF) is most commonly reported in IU/mL. Labs in different countries may use other units — you can convert between them with BloodId's blood test unit converter.
- Where do Rheumatoid Factor (RF) reference ranges come from?
- BloodId uses ABIM standard reference ranges and educational information from MedlinePlus (see our methodology). Reference ranges still vary by lab, age, and sex, so always compare against your own report.
- Can I track Rheumatoid Factor (RF) over time?
- Yes. Upload results from any lab and BloodId charts your Rheumatoid Factor (RF) over time against its reference range, so you can see whether the trend is rising, falling, or stable.
Related biomarkers
Source: MedlinePlus, U.S. National Library of Medicine
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