Baseline characteristics of nbDMARD and TNFi-treated patients
| First TNFi drug | ||||||||
|---|---|---|---|---|---|---|---|---|
| nbDMARD (n=3673) | All TNFi (n=12 937) | p Value* | Etanercept (n=4516) | Adalimumab (n=4362) | Infliximab (n=3363) | Certolizumab (n=696) | p Value† | |
| Demographic features | ||||||||
| Age, mean (SD) years | 60 (12) | 56 (12) | <0.001 | 56 (12) | 57 (12) | 56 (12) | 56 (12) | 0.012 |
| Gender, % female | 72 | 76 | <0.001 | 77 | 76 | 76 | 76 | 0.62 |
| Rheumatoid factor-positive, % | 2135 (58) | 8199 (63) | <0.001 | 2883 (64) | 2688 (62) | 2250 (67) | 378 (58) | <0.001 |
| Ethnicity | ||||||||
| White | 2952 (80) | 10 467 (81) | <0.001 | 3638 (81) | 3588 (83) | 2795 (83) | 446 (64) | |
| Black | 24 (0.6) | 86 (0.7) | 28 (0.6) | 34 (0.8) | 19 (0.6) | 5 (0.7) | 0.42 | |
| South Asian | 32 (0.9) | 228 (2) | 82 (2) | 73 (2) | 65 (2) | 8 (1) | ||
| Chinese | 2 (0.1) | 31 (0.2) | 9 (0.2) | 12 (0.3) | 9 (0.2) | 1 (0.2) | ||
| Other | 15 (0.4) | 117 (0.9) | 36 (0.8) | 31 (0.7) | 41 (1.2) | 9 (1) | ||
| Not recorded | 648 (18) | 2002 (16) | 723 (16) | 624 (14) | 428 (13) | 227 (32) | ||
| Smoking history, n (%) | ||||||||
| Current smoker | 869 (24) | 2762 (21) | <0.001 | 911 (20) | 980 (23) | 734 (22) | 137 (20) | <0.001 |
| Former smoker | 1452 (40) | 4888 (38) | 1728 (38) | 1660 (38) | 1274 (38) | 226 (33) | ||
| Never smoked | 1334 (36) | 5159 (40) | 1830 (41) | 1683 (38) | 1338 (40) | 308 (44) | ||
| Not recorded | 18 (0.5) | 128 (1) | 47 (1) | 39 (1) | 17 (0.5) | 25 (3) | ||
| Disease duration, median (IQR) | 6 (1–15) | 10 (5–18) | <0.001 | 11 (5–19) | 10 (5–18) | 12 (6–19) | 5 (2–12) | <0.001 |
| DAS28 score, mean (SD) | 5.1 (1.3) | 6.5 (1) | <0.001 | 6.5 (1) | 6.4 (1) | 6.6 (1) | 5.9 (1) | <0.001 |
| HAQ score, mean (SD) | 1.5 (0.8) | 2.0 (0.6) | <0.001 | 2.0 (0.6) | 1.9 (0.6) | 2.1 (0.6) | 1.5 (0.8) | <0.001 |
| Comorbidity, n (%) | ||||||||
| None | 1544 (42) | 6031 (47) | <0.001 | 2026 (45) | 2060 (47) | 1582 (47) | 363 (52) | 0.001 |
| 1 comorbidity | 1270 (35) | 4397 (34) | 1522 (34) | 1476 (34) | 1177 (35) | 222 (32) | ||
| 2 comorbidity | 596 (16) | 1839 (14) | 701 (15) | 601 (14) | 457 (14) | 80 (11) | ||
| ≥3 comorbidities | 263 (7) | 670 (5) | 267 (6) | 225 (5) | 147 (4) | 31 (5) | ||
| Treatment-related factors | ||||||||
| Number of prior nbDMARDS, median (IQR) | 2 (1–3) | 3 (3–5) | <0.001 | 4 (3–5) | 3 (2–4) | 4 (3–5) | 3 (2–3) | <0.001 |
| On methotrexate, n (%) | 2449 (67) | 7932 (61) | <0.001 | 1921 (43) | 2554 (59) | 2983 (89) | 474 (68) | <0.001 |
| On sulfasalazine, n (%) | 1245 (34) | 2395 (18) | <0.001 | 682 (15) | 971 (22) | 513 (15) | 229 (33) | <0.001 |
| On leflunomide, n (%) | 495 (13) | 1182 (9) | <0.001 | 377 (8) | 495 (11) | 244 (7) | 66 (9) | <0.001 |
| On azathioprine, n (%) | 93 (2) | 309 (2) | 0.62 | 123 (3) | 91 (2) | 92 (3) | 3 (0.4) | 0.001 |
| On minocycline, n (%) | 1 (0.03) | 18 (0.1) | 0.08 | 5 (0.1) | 7 (0.2) | 6 (0.2) | 0 | 0.63 |
| On hydroxychloroquine, n (%) | 639 (17) | 1842 (14) | <0.001 | 519 (11) | 716 (16) | 348 (10) | 259 (37) | <0.001 |
| Baseline steroid use, n (%) | 836 (23) | 5348 (41) | <0.001 | 2018 (45) | 1617 (37) | 1541 (46) | 172 (25) | <0.001 |
*p Value represents the significance of differences between the nbDMARD and TNFi cohorts using χ2 tests for categorical outcomes and Wilcoxon rank sum tests for continuous variables.
†p Value represents the significance of differences between the four TNFi drugs using χ2 tests for categorical outcomes and Kruskal-Wallis rank tests for continuous variables. Values <1 are represented up to one decimal point.
DAS28, 28 joint count Disease Activity Score; HAQ, Health Assessment Questionnaire; nbDMARDs, non-biological disease-modifying antirheumatic drugs; TNFi, tumour necrosis factor-α inhibitor.