Nested case–control study population characteristics by autoantibody status (RF and/or anti-CCP2 positive)
| Descriptive variable | Anti-CCP2(+) (n=40) | High titre RF(+) (n=27) | RF(−) and anti-CCP2(−) (n=69) | p Values* |
|---|---|---|---|---|
| Age at study visit (mean±SD) | 43.7±15.4 | 48.1±13.2 | 46.5±13.9 | 0.45 |
| Non-Hispanic whites, n (%) | 25 (62.5) | 23 (85.2) | 47 (68.1) | 0.12 |
| Sex, n (% female) | 30 (75.0) | 17 (63.0) | 52 (75.4) | 0.44 |
| Education, n (% >high school) | 29 (72.5) | 23 (85.2) | 54 (78.3) | 0.47 |
| Income, n (% ≥$40 000 annually) | 28 (70.0) | 23 (85.2) | 46 (66.7) | 0.19 |
| Shared epitope, n (% positive) | 24 (60.0) | 11 (40.7) | 44 (63.8) | 0.11 |
| Ever smoker, n (% yes) | 11 (27.5) | 11 (40.7) | 30 (43.5) | 0.24 |
| Current smoker, n (% yes) | 2 (5.0) | 3 (11.1) | 6 (8.7) | 0.66 |
*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.