Comparison of baseline variables between patients with or without registered dispensations of antibiotics in the year prior to anti-TNF initiation
| Variable | Total (n=1946) | With prior antibiotics (n=1593) | No prior antibiotics (n=353) | P value |
| Age, years | 29 (24) | 29 (24) | 27 (23) | 0.59 |
| Male, n (%) | 1035 (53) | 826 (52) | 211 (60) | 0.01 |
| BMI*, kg/m² | 22 (6.2) | 22 (6) | 22 (6) | 0.53 |
| Adalimumab, n (%) | 1065 (55) | 868 (54) | 197 (56) | 0.7 |
| Prior anti-TNF, n (%) | 567 (29) | 493 (31) | 74 (21) | <0.001 |
| Crohn’s, n (%) | 1595 (82) | 1307 (82) | 288 (82) | 0.9 |
| Prior related surgery | 526 (27) | 437 (27) | 89 (25) | 0.43 |
| Recent prior hospitalisations | 886 (46) | 558 (46) | 328 (45) | 0.06 |
| Laboratory results, median (IQR) | ||||
| Haemoglobin*, g/dL | 12.8 (2.2) | 12.7 (2.2) | 13 (2.2) | 0.07 |
| WBC*,×109/L | 7.3 (3.1) | 7.3 (3.1) | 7 (3.1) | 0.08 |
| Platelets*, ×109/L | 284 (119) | 285 (121) | 282 (105) | 0.3 |
| CRP*, mg/dL | 0.9 (2) | 0.9 (2.1) | 0.8 (1.7) | 0.14 |
| Albumin*, g/dL | 4.1 (0.6) | 4.1 (0.5) | 4.1 (0.5) | 0.13 |
| Prior/concomitant medications, n (%) | ||||
| Corticosteroids | 236 (12) | 197 (12) | 39 (11) | 0.55 |
| Thiopurines | 856 (44) | 713 (45) | 134 (41) | 0.16 |
| Methotrexate | 133 (7) | 116 (7) | 17 (5) | 0.12 |
| 5-ASA | 572 (29) | 481 (30) | 91 (26) | 0.11 |
| Time (days) to antibody monitoring | ||||
| Time to first measure, days | 675 (1136) | 611 (1249) | 406 (923) | <0.001 |
| Time to end of follow-up, days | 651 (1175) | 703 (1227) | 475 (929) | <0.001 |
*Data for these variables were not available for all included patients. Availability of each variable was as follows: BMI, 93%; haemoglobin, 98.9%; WBC, 98.9%; platelets, 98.9%; CRP, 80.3%; albumin, 94.3%.
anti-TNF, anti-tumour necrosis factor ; 5-ASA, 5-aminosalicylic acid; BMI, body mass index; CRP, C reactive protein; ; WBC, white blood cells.