Study population characteristics by autoantibody status (RF and anti-CCP2 positive) of the SERA cohort at their baseline visit with complete records
| Descriptive variable | Anti-CCP2(+) (n=44) | RF(+) (n=106) | RF(−) and anti-CCP2(−) (n=2009) | p Value* |
|---|---|---|---|---|
| Age at baseline visit (mean±SD) | 44.0±15.8 | 46.8±14.5 | 44.1±14.0 | 0.16 |
| Non-Hispanic whites (%) | 63.6 | 69.8 | 81.1 | <0.01 |
| Sex (% female) | 72.7 | 72.6 | 68.6 | 0.58 |
| Education (% >high school) | 68.2 | 84.9 | 81.8 | 0.04 |
| Income (%≥$40 000 annually) | 63.6 | 84.0 | 75.7 | 0.02 |
| Shared epitope (% positive) | 61.4 | 50.0 | 53.2 | 0.45 |
| Ever smoker (% yes) | 31.8 | 40.6 | 38.9 | 0.59 |
| Current smoker (% yes) | 6.8 | 10.4 | 12.2 | 0.49 |
*p Value calculated is an omnibus test of difference; analysis of variance for continuous variables, and χ2 test for categorical variables.
anti-CCP, anti-cyclic citrullinated peptide; RF, rheumatoid factor; SERA, Studies of the Etiology of RA.