Baseline characteristics of the 258 patients initiating the first TNFi, the 127 patients switching for a second TNFi and the rest of the cohort
| Baseline characteristics* | Patients receiving a TNFi over the 5 years of follow-up N=258 | Patients switching to a second TNFi over the 5 years of follow-up N=127 | Patients receiving usual care† N=450 | P value‡ |
| Age (years) | 34.0 (9.0) | 35.3 (8.7) | 34.6 (8.4) | 0.53 |
| Sex (male) | 113 (43.8) | 40 (31.5) | 213 (47.3) | 0.35 |
| Symptoms duration (years) | 1.5 (0.9) | 1.6 (0.9) | 1.5 (0.9) | 0.53 |
| Employment (blue collar) | 42/256 (16.4) | 23/126 (18.3) | 63/445 (14.3) | 0.42 |
| Education (university) | 133 (51.6) | 64 (50.4) | 284/445 (63.8) | 0.001 |
| HLA-B27 positive | 147 (57.0) | 62 (48.8) | 263/448 (58.7) | 0.65 |
| MRI sacroiliitis positive | 105/253 (41.5) | 39/125 (31.2) | 130/438 (29.7) | 0.002 |
| Radiographic sacroiliitis positive | 57/254 (22.4) | 17 (13.4) | 55/439 (12.5) | <0.001 |
| History of good NSAID response | 221/257 (86.0) | 104/126 (82.5) | 376/444 (84.7) | 0.64 |
| History of arthritis | 89/256 (34.8) | 37/125 (29.6) | 102/446 (22.9) | <0.001 |
| History of dactylitis | 39/257 (15.2) | 16/126 (11.9) | 58/447 (13.0) | 0.41 |
| CRP (mg/L) | 12.5 (19.1) | 10.5 (19.8) | 5.3 (7.8) | <0.001 |
| ASDAS-CRP | 3.1 (0.9) | 3.2 (0.8) | 2.4 (0.9) | <0.001 |
| BASDAI (range 0–10) | 5.3 (1.7) | 5.9 (1.5) | 4.0 (2.0) | <0.001 |
| BASFI (range 0–10) | 4.0 (2.2) | 4.6 (2.1) | 2.5 (2.2) | <0.001 |
| Centre in which TNFi prescription rate was >30% over follow-up | 201 (77.9) | 97 (76.4) | 237 (52.7) | <0.001 |
| Presence of at least one objective sign of inflammation**** | 159/252 (63.1) | 60/125 (48.0) | 192/426 (45.1) | <0.001 |
***Comparing the first TNFi to the rest of the cohort.
*Values are presented as mean (SD) and n (%) for continuous and categorical variables, respectively.
†Usual care=any (non-biological) treatment other than TNFi.
‡Objective sign of inflammation is the presence of at least a systemic increased CRP (≥6 mg/L) or local inflammation (MRI sacroiliitis) or structural damage of the sacroiliac joint.
ASDAS-CRP, Ankylosing Spondylitis Disease Activity Score using CRP; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; CRP, C reactive protein; NSAID, non-steroidal anti-inflammatory drugs; TNFi, tumour necrosis factor inhibitor.