Key clinical point: The incidence of RF-negative rheumatoid arthritis (RA) increased, while RF-positive RA decreased among adults in the United States between 2005 and 2014, compared with earlier decades.

Major finding: Overall RA incidence was stable between 2005 and 2014; however, 51% of RA patients tested were positive for rheumatoid factor during this time, compared with 69% of patients tested between 1985 and 1994, and 69% of those tested between 1995 and 2004 (P less than 0.001).

Study details: The data come from RA patients identified between January 1, 1985, and December 31, 2014, via the population-based Rochester Epidemiology Project in Minnesota.

Disclosures: The study was supported in part by the National Institutes of Health. The researchers had no financial conflicts to disclose.