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Rheumatoid Factor (RF) Unit Converter
Rheumatoid Factor (RF) is an autoantibody, typically of the IgM class, that targets the Fc portion of IgG. It is a key biomarker for the diagnosis and prognosis of **Rheumatoid Arthritis (RA)** and Sjögren’s syndrome.
Because RF is a mixture of polyclonal antibodies, results are reported in activity units standardized against WHO reference preparations. This converter facilitates switching between the standard International Units (IU/mL) and the numerically equivalent SI unit (kIU/L).
Standard Units
RecommendedInternational Units per milliliter (Numerically equivalent to kIU/L).
Other Variations
Clinical Context
Reference Ranges:
• Normal (Negative): < 14 – 20 IU/mL (varies by laboratory).
• Positive: Levels above the lab-specific cut-off. High titers (>3x ULN) have higher specificity for Rheumatoid Arthritis.
Conversion Logic:
1 IU/mL = 1 kIU/L (SI).
1 IU/mL = 1 U/mL (typically synonymous in clinical reports).
Clinical References
How to Use This Converter
Follow these steps to normalize RF values.
Enter Values
Input your laboratory results into the corresponding unit field (e.g., IU/mL).
Automatic Conversion
The calculator instantly updates all other fields. For RF, unit values are numerically identical across standard reporting formats.
Reset
Use the Clear button to reset all fields.
Frequently Asked Questions
Yes. 1 International Unit per milliliter is numerically the same as 1,000 International Units (kIU) per liter.
Not necessarily. RF can be elevated in other autoimmune diseases, infections, or even in healthy older adults. Diagnosis requires clinical evaluation.