Baseline characteristics of patients with undifferentiated arthritis
| Characteristics | No progression to RA (n = 25) | Progression to RA (n = 80) | p Value |
| Age (years), mean (SD) | 44 (15) | 46 (14) | 0.51 |
| Female sex | 18 (72) | 63 (79) | 0.48 |
| Current smoker | 2 (8) | 13 (16) | 0.30 |
| RA family history | 6 (24) | 32 (40) | 0.15 |
| Symptom duration | 0.21 | ||
| <6 Weeks | 3 (12) | 0 (0) | |
| 6 Weeks to 3 months | 6 (24) | 22 (28) | |
| 3–6 Months | 9 (36) | 28 (35) | |
| >6 Months | 7 (28) | 30 (38) | |
| Number of tender joints, median (IQR) | 4 (2–12) | 22 (12–30) | <0.001* |
| Number of swollen joints, median (IQR) | 1 (0–7) | 12 (6–20) | <0.001* |
| Joint localisation | 0.19 | ||
| Small joints only | 10 (40) | 20 (25) | |
| Large joints only | 3 (12) | 1 (1) | |
| Small and large joints | 12 (48) | 59 (74) | |
| Joint distribution | 0.22 | ||
| Upper extremities only | 8 (32) | 8 (10) | |
| Lower extremities only | 3 (12) | 0 (0) | |
| Upper and lower extremities | 14 (56) | 72 (90) | |
| Symmetric joint involvement | 16 (64) | 71 (89) | 0.31 |
| Morning stiffness (h), mean (SD) | 1.6 (1.6) | 3.4 (6.5) | 0.17 |
| C-reactive protein (mg/l), mean (SD) | 5.2 (12.4) | 13.4 (24.3) | 0.11 |
| ESR (mm/h), mean (SD) | 15.6 (13.7) | 22.8 (20.8) | 0.11 |
| RF positive | 2 (8) | 28 (35) | 0.001* |
| Anti-CCP positive | 2 (8) | 35 (44) | 0.001* |
| HAQ score, mean (SD) | 0.52 (0.61) | 0.94 (0.67) | 0.006* |
| RADAI score, mean (SD) | 3.8 (1.8) | 5.0 (1.8) | 0.003* |
| DAS28 (ESR) score, mean (SD) | 3.4 (1.9) | 5.6 (1.4) | <0.001* |
| Erosive disease | 2 (8) | 19 (24) | 0.09 |
Values are shown as number (%) unless stated otherwise.
Anti-CCP, anti-cyclic citrullinated peptide; DAS28, Disease Activity Score 28; ESR, erythrocyte sedimentation rate; HAQ, Health Assessment Questionnaire; IQR, interquartile range; RA, rheumatoid arthritis; RADAI, Rheumatoid Arthritis Disease Activity Index; RF, rheumatoid factor; SD, standard deviation.