| A: Individual Characteristic of IBP |
| Morning stiffness >30 min | 171 (63.3) | 216 (56.4) | 1.34* | 1.10 | 63.3 | 43.6 | 44.2 | 62.8 | 1.12 | 0.84 |
| Improve with exercise, not with rest | 91 (33.7) | 114 (29.8) | 1.20 | | 33.7 | 70.2 | 44.4 | 60.0 | 1.13 | 0.94 |
| Alter. buttock pain | 86 (31.9) | 110 (28.7) | 1.16 | | 31.9 | 71.3 | 43.9 | 59.7 | 1.11 | 0.96 |
| Insidious onset | 184 (68.1) | 241 (62.9) | 1.26 | | 68.1 | 37.1 | 43.3 | 62.3 | 1.08 | 0.86 |
| Awakening 2nd half night | 149 (55.2) | 163 (42.6) | 1.66*** | 1.53** | 55.2 | 57.4 | 47.8 | 64.5 | 1.30 | 0.78 |
| Response to NSAIDs | 182 (67.4) | 217 (56.7) | 1.58*** | 1.46** | 67.4 | 43.3 | 45.6 | 65.4 | 1.19 | 0.75 |
| B: Combination of IBP characteristics |
| Calin criteria | 98 (36.1) | 99 (25.8) | 1.63** | – | 36.3 | 74.2 | 49.7 | 62.3 | 1.41 | 0.86 |
| Berlin criteria | 173 (64.1) | 194 (50.7) | 1.74** | – | 64.1 | 49.3 | 47.1 | 66.1 | 1.26 | 0.73 |
| ASAS criteria | 85 (31.5) | 74 (19.3) | 1.92*** | – | 31.5 | 80.7 | 53.5 | 62.3 | 1.63 | 0.85 |
| Night + NSAID response (2/2) | 108 (40) | 109 (28.5) | 1.68** | – | 40.0 | 71.5 | 49.8 | 62.8 | 1.40 | 0.84 |
| Calin + Night + NSAID response (6/7) | 58 (21.5) | 45 (11.7) | 2.06** | – | 21.5 | 88.3 | 56.3 | 61.5 | 1.84 | 0.89 |
| Berlin + NSAID response (3/5) | 154 (57.0) | 153 (39.9) | 2.00*** | – | 57.0 | 60.1 | 50.2 | 66.5 | 1.43 | 0.72 |
| ASAS + NSAID response (5/6) | 66 (24.4) | 51 (13.3) | 2.11*** | – | 24.4 | 86.7 | 56.4 | 61.9 | 1.83 | 0.87 |