Table 1. Clinical characteristics of patients on the training, internal test, external test, and prospective test sets.
| Characteristics | All sets (n=541) | Training set (n=328) | Internal test set (n=72) | External test set (n=54) | Prospective test set (n=87) | P value |
|---|---|---|---|---|---|---|
| Age (years) | 37.0±16.0 | 36.9±17.0 | 36.7±15.1 | 36.6±12.7 | 38.2±14.4 | 0.732 |
| Sex | 0.007 | |||||
| Female | 241 (44.5) | 144 (44.0) | 30 (41.7) | 16 (29.6) | 51 (58.6) | |
| Male | 300 (55.5) | 184 (56.0) | 42 (58.3) | 38 (70.4) | 36 (41.4) | |
| Disease duration# | 12.0 (5.0, 48.0) | 18.5 (6.0, 60.0) | 12.0 (4.5, 60.0) | 7.0 (1.5, 36.0) | 12.0 (4.2, 48.0) | 0.136 |
| Structural damage | 0.336 | |||||
| Positive | 303 (56.0) | 177 (53.9) | 39 (54.2) | 36 (66.7) | 51 (58.6) | |
| Negative | 238 (44.0) | 151 (46.1) | 33 (45.8) | 18 (33.3) | 36 (41.4) | |
| SpA features | ||||||
| Arthritis | 179 (33.1) | 95 (28.9) | 17 (23.6) | 41 (75.9) | 26 (29.9) | <0.001 |
| Heel enthesitis | 31 (5.7) | 0 | 0 | 31 (57.4) | 0 | <0.001 |
| Uveitis | 1 (0.1) | 0 | 0 | 1 (1.9) | 0 | 0.029 |
| Dactylitis | 14 (2.6) | 0 | 0 | 12 (22.2) | 2 (2.3) | <0.001 |
| Psoriasis | 3 (0.6) | 1 (0.3) | 1 (1.4) | 0 | 1 (1.1) | 0.544 |
| Crohn’s disease or UC | 4 (0.7) | 2 (0.6) | 0 | 1 (1.9) | 1 (1.1) | 0.632 |
| Good response to NSAIDs | 334 (61.7) | 234 (71.3) | 58 (80.5) | 14 (25.9) | 28 (32.2) | <0.001 |
| Family history of axSpA | 58 (10.7) | 27 (8.2) | 18 (25.0) | 8 (14.8) | 5 (5.7) | <0.001 |
| Elevated CRP concentration | 181 (33.5) | 114 (34.8) | 22 (30.6) | 32 (59.3) | 13 (14.9) | <0.001 |
| Classification | ||||||
| AxSpA | 261 (48.2) | 138 (42.1) | 45 (62.5) | 25 (46.3) | 53 (60.9) | |
| Non-axSpA | 280 (51.8) | 190 (57.9) | 27 (37.5) | 29 (53.7) | 34 (39.1) | |
Data are presented as median (Q1, Q3), mean ± standard deviation or number (%). P values represent the statistical differences among the training, internal, external, and prospective test sets. In the SpA features, data are numbers of positive patients with percentages in parentheses. M, months; UC, ulcerative colitis; NSAIDs, nonsteroidal anti-inflammatory drugs; axSpA, axial spondyloarthritis; CRP, C-reactive protein.