Rheumatoid factor is positive in approximately what percentage of rheumatoid arthritis patients?

Rheumatoid factor is positive in approximately what percentage of rheumatoid arthritis patients?

• A. 75-80%
• B. 60-70%
• C. 90-95%
• D. 40-50%

Answer: (A)

Rheumatoid factor positivity is common in rheumatoid arthritis, occurring in about three quarters of patients. This autoantibody (usually IgM against the Fc portion of IgG) supports the diagnosis but is not specific to RA and can be absent in some patients or present in other conditions. Because of that, the typical prevalence is around 75–80%, making the 75–80% range the best fit. The other ranges are either too low or too high for how often RF is positive in RA.

Rheumatoid factor positivity is common in rheumatoid arthritis, occurring in about three quarters of patients. This autoantibody (usually IgM against the Fc portion of IgG) supports the diagnosis but is not specific to RA and can be absent in some patients or present in other conditions. Because of that, the typical prevalence is around 75–80%, making the 75–80% range the best fit. The other ranges are either too low or too high for how often RF is positive in RA.