Table 1.
Baseline participant characteristics overall and by IL-33 quartile
| Measure | Overall (n = 2835) | Quartile 1 | Quartile 2 | Quartile 3 | Quartile 4 | P-value |
|---|---|---|---|---|---|---|
| Age, mean (s.d.), years | 65 (11) | 65 (10) | 65 (11) | 65 (11) | 63 (12) | <0.001 |
| Sex, n (%) | 0.002 | |||||
| Female | 342 (12) | 69 (10) | 88 (12) | 73 (10) | 112 (16) | |
| Male | 2493 (88) | 640 (90) | 621 (88) | 636 (90) | 596 (84) | |
| Race, n (%) | 0.551 | |||||
| White | 2193 (77) | 542 (76) | 546 (77) | 557 (79) | 548 (77) | |
| Black/AA | 447 (16) | 126 (18) | 109 (15) | 105 (15) | 107 (15) | |
| Other | 195 (7) | 41 (6) | 54 (8) | 47 (7) | 53 (8) | |
| Smoking status, n (%) | <0.001 | |||||
| Current | 681 (24) | 184 (26) | 187 (26) | 166 (23) | 144 (20) | |
| Former | 1464 (52) | 374 (53) | 340 (48) | 397 (56) | 353 (50) | |
| Never | 549 (19) | 121 (17) | 124 (17) | 115 (16) | 189 (27) | |
| Unknown | 141 (5) | 30 (4) | 58 (8) | 31 (4) | 22 (3) | |
| BMI, mean (s.d.), kg/m2 | 28 (6) | 29 (5) | 29 (6) | 28 (6) | 28 (6) | 0.335 |
| DAS28, mean (s.d.) | 3.7 (1.5) | 3.8 (1.5) | 3.9 (1.6) | 3.7 (1.6) | 3.5 (1.5) | 0.001 |
| DAS state, n (%) | 0.002 | |||||
| Remission/low | 1152 (41) | 279 (39) | 258 (36) | 286 (40) | 329 (46) | |
| Moderate/high | 1631 (58) | 414 (58) | 435 (61) | 408 (58) | 374 (53) | |
| Unknown | 52 (2) | 16 (2) | 16 (2) | 15 (2) | 5 (1) | |
| Methotrexate use, n (%) | 1239 (54) | 323 (54) | 314 (56) | 311 (56) | 291 (50) | 0.206 |
| Prednisone use, n (%) | 929 (40) | 255 (42) | 244 (43) | 220 (39) | 210 (36) | 0.064 |
| Anti-TNF use, n (%) | 652 (23) | 185 (26) | 173 (24) | 147 (21) | 147 (21) | 0.034 |
| Anti-CCP positive, n (%) | 1998 (77) | 509 (77) | 493 (81) | 487 (77) | 509 (75) | 0.132 |
| RF positive, n (%) | 1933 (77) | 501 (77) | 477 (82) | 468 (77) | 487 (74) | 0.007 |
| RA disease duration, mean (s.d.), years | 11 (11) | 12 (12) | 12 (11) | 11 (11) | 11 (11) | 0.055 |
| COPD, n (%) | 450 (16) | 137 (19) | 120 (17) | 93 (13) | 100 (14) | 0.006 |
P-values generated using Kruskal–Wallis tests for continuous measures, χ2 tests for categorical measures. AA: African American; COPD: chronic obstructive pulmonary disease.