From the Research
Rheumatoid factor (RF) has a sensitivity of 65% and specificity of 90% for rheumatoid arthritis, as reported in the most recent study 1. The sensitivity and specificity of RF can vary depending on the population being tested and the criteria used to define a positive result.
- The study found that IgM-RF was the most sensitive subtype, with a sensitivity of 65%, followed by IgG-ACPA, with a sensitivity of 59.5% 1.
- The specificity of RF was found to be 90%, with IgG-ACPA and IgA-ACPA having specificities greater than 98% 1.
- A high RF titer is typically considered to be above 50 IU/mL, but the exact cutoff value can vary depending on the laboratory and the specific assay used.
- RF testing should always be interpreted alongside clinical symptoms and other diagnostic markers, such as anti-citrullinated protein antibodies (ACPA/anti-CCP), which has higher specificity for rheumatoid arthritis 1, 2.
- The presence of both elevated RF and positive anti-CCP significantly increases diagnostic accuracy, and RF positivity often correlates with more aggressive disease, extra-articular manifestations, and worse long-term outcomes 1, 2.
- It is essential to consider RF testing as part of a comprehensive clinical assessment rather than as a standalone diagnostic test for rheumatoid arthritis.
- The use of multiple biomarkers, including RF, ACPA, and other autoantibodies, can increase the diagnostic power of autoimmune diagnostics and support clinical decision-making 1, 2.