Long-Term RA Risk Greater With Elevated Rheumatoid Factor

The long-term risk of rheumatoid arthritis (RA) is up to 26-fold greater and there is up to a 32% 10-year absolute risk of RA in persons in the general population who have elevated rheumatoid factor (RF) levels, according to a study reported in the British Medical Journal. These findings may lead to revision of guidelines for early referral to a rheumatologist and early arthritis clinics based on RF testing.

Nielsen and colleagues conducted a prospective cohort study of 9712 white Danish persons from the general population aged 20 to 100 years without RA at study entry. The main outcome measure was RA according to baseline plasma IgM RF level categories of 25 to 50 IU/mL, 50.1 to 100 IU/mL, and higher than 100 IU/mL, versus lower than 25 IU/mL.

RF levels were similar in persons aged 20 to 100 years. During 187,659 person-years, RA developed in 183 persons. In healthy persons, a doubling in levels of RF was associated with a 3.3-fold increased risk of developing RA; there was a similar trend for most other autoimmune rheumatologic diseases. The cumulative incidence of RA increased with increasing RF category. The highest absolute 10-year risk of RA of 32% was observed women aged 50 to 69 years who smoked cigarettes and had RF levels higher than 100 IU/mL.