(HealthDay News) – Individuals in the general population with elevated levels of rheumatoid factor have a significantly increased risk of developing rheumatoid arthritis, according to a study published online Sept 6 in BMJ.
Sune F. Nielsen, PhD, from the Copenhagen University Hospital in Denmark, and colleagues conducted a prospective cohort study involving 9,712 white Danish individuals in the Copenhagen general population, aged 20–100 years, to examine whether elevated concentration of rheumatoid factor correlates with long-term development of rheumatoid arthritis.
The researchers found that 183 individuals developed rheumatoid arthritis during 187,659 person-years. A doubling in levels of rheumatoid factor in healthy individuals correlated with a 3.3-fold increase in the risk of developing rheumatoid arthritis, with a similar trend noted for most other autoimmune rheumatic diseases. With increasing rheumatoid factor category the cumulative incidence of rheumatoid arthritis increased. Compared with a rheumatoid factor level of <25 IU/mL, the multivariable adjusted hazard ratio was 3.6 for levels of 25–50 IU/mL; 6.0 for 50.1–100 IU/mL; and 26 for >100 IU/mL. Fifty- to 69-year-old women who smoked and had rheumatoid factor levels above 100 IU/mL had the highest absolute 10-year risk of rheumatoid arthritis (32%).
“Individuals in the general population without rheumatoid arthritis but with an elevated plasma level of rheumatoid factor have up to 26-fold greater long-term risk of developing rheumatoid arthritis, and up to 32% 10-year absolute risk of rheumatoid arthritis,” the authors write.