Patient characteristics of 1987 undifferentiated arthritis patients and 2010 undifferentiated arthritis patients, at first presentation
| Characteristic | 1987 Undifferentiated arthritis (n=1166) | 2010 Undifferentiated arthritis (n=776) | p Value |
|---|---|---|---|
| Age, mean±SD, years | 51.6±17.1 | 50.3±17.2 | 0.12 |
| Female sex | 699 (59.9) | 443 (57.1) | 0.21 |
| BMI, mean±SD, kg/m2 | 25.9±4.3 | 25.6±4.4 | 0.26 |
| Current or past smoker | 286 (28.0) | 197 (29.1) | 0.97 |
| Onset of symptoms | |||
| (Sub)acute | 657 (58.8) | 465 (62.4) | 0.12 |
| Gradual | 460 (41.2) | 280 (37.6) | |
| Morning stiffness, median (IQR), min | 30 (0–60) | 30 (0–60) | 0.06 |
| 0–29 | 457 (41.0) | 337 (45.6) | 0.14 |
| 30–59 | 190 (17.0) | 117 (15.8) | |
| ≥60 | 468 (42.0) | 285 (38.6) | |
| Symptom duration, median (IQR), weeks | 15.7 (6.9–31.9) | 13.4 (5.3–29.2) | 0.01 |
| Localisation of affected joints | |||
| Small joints hands/feet | 908 (81.1) | 631 (84.8) | 0.04 |
| Localisation of affected joints | |||
| Symmetrical | 563 (54.0) | 328 (47.7) | 0.01 |
| Localisation of affected joints | |||
| Upper extremities | 722 (72.1) | 507 (75.7) | 0.10 |
| Swollen joint count, median (IQR) | 3 (1–7) | 2 (1–5) | <0.001 |
| 0–3 joints | 607 (53.1) | 494 (65.3) | <0.001 |
| 4–10 joints | 364 (31.8) | 218 (28.8) | |
| >10 joints | 172 (15.0) | 44 (5.8) | |
| Tender joint count, median (IQR) | 5 (2–12) | 2 (1–6) | <0.001 |
| 0–3 joints | 301 (40.2) | 266 (59.2) | <0.001 |
| 4–10 joints | 223 (29.8) | 158 (35.2) | |
| >10 joints | 225 (30.0) | 25 (5.6) | |
| ESR, median (IQR), mm/h | 19 (8–39) | 16 (8–36) | 0.02 |
| CRP, median (IQR), mg/l | 9 (3–24.5) | 8 (3–23) | 0.29 |
| RF positive | 294 (25.5) | 76 (9.9) | <0.001 |
| Low positive | 118 (10.2) | 32 (4.2) | 0.83 |
| High positive | 176 (15.3) | 44 (5.7) | |
| Anti-CCP-2 positive | 234 (24.1) | 61 (9.6) | <0.001 |
| Low positive | 44 (4.5) | 44 (6.9) | <0.001 |
| High positive | 190 (19.6) | 17 (2.7) | |
| HAQ, mean±SD | 0.8±0.7 | 0.7±0.6 | 0.01 |
| 2010 Criteria score, mean±SD | 4.9 (2.4) | 3.2 (1.4) | <0.001 |
Except where indicated otherwise, values are the number (%) of patients.
interquartile range (IQR) Localisation of affected joint: ‘upper joints’ stands for upper joints with or without involvement of the lower joints, whereas ‘small joints’ stands for smaller joints with or without involvement of the large joints.
In the group of all patients with undifferentiated arthritis, some data were missing, as follows: for body mass index, n=351; for smoking, n=146; for onset of symptoms, n=48; for morning stiffness, n=51; for symptom duration, n=95; for small joints involved, n=46, for symmetrical joint involvement, n=123; for upper extremity joints involved, n=164; n=25; for erythrocyte sedimentation rate (ESR), n=8; for C-reactive protein (CRP), n=81; for rheumatoid factor (RF), n=11; for citrullinated protein antibodies (CCP), n=197; for health assessment questionnaire (HAQ) score, n=245.
A χ2 square test was used for nominal variables and the Student's t test or Mann–Whitney U-test for continuous variables. Student's t test was performed when variables are presented as mean and a Mann–Whitney U-test was performed when variables are presented as median.
RF, rheumatoid factor.