Table 1.
Baseline characteristics of the total population of UA patients and for the patients that did and did not develop RA within one year
| Characteristic | Total (n = 518) |
Developed RA (n = 160) |
Did not develop RA (n = 358) |
P | LR+ | LR- |
|---|---|---|---|---|---|---|
| Female gender n (%) | 305 (59) | 111 (69) | 194 (54) | 0.001 | 1.3 | 0.67 |
| Age in years (Mean ± SD) | 50.6 ± 16.5 | 56.3 ± 15 | 48 ± 16.5 | < 0.001 | - | - |
| Symptom duration at inclusion in months (Mean ± SD) | 4.9 ± 5.5 | 5.9 ± 6 | 4.4 ± 5.1 | 0.002 | - | - |
| Morning stiffness (Mean ± SD) | 55.7 ± 89.9 | 82.9 ± 111.4 | 43.6 ± 75.6 | < 0.001 | - | - |
| Tender joint count (Mean ± SD) | 6.5 ± 6.3 | 9.5 ± 7.4 | 5.1 ± 5.3 | < 0.001 | - | - |
| Swollen joint count (Mean ± SD) | 3.8 ± 4 | 5.7 ± 5.1 | 2.9 ± 3.1 | < 0.001 | - | - |
| HAQ score (Mean ± SD) | 0.76 ± 0.6 | 0.9 ± 0.6 | 0.7 ± 0.6 | < 0.001 | - | - |
| ESR (mm/hr) (Mean ± SD) | 28.9 ± 24.4 | 36.8 ± 23.7 | 25.3 ± 23.9 | < 0.001 | - | - |
| CRP (mg/L) (Mean ± SD) | 20.6 ± 28.2 | 26.5 ± 29.1 | 17.9 ± 27.4 | < 0.001 | - | - |
| RF positivity n (%) | 125 (24.2) | 76 (47.5) | 49 (13.7) | < 0.001 | 3.5 | 0.61 |
| ACPA positivity n (%) | 114 (23.4) | 76 (50) | 38 (11.3) | < 0.001 | 4.4 | 0.56 |
| **Having erosive joints in hands and/or feet n (%) | 148 (28.6) | 67 (41.9) | 81 (22.6) | < 0.001* | 1.8 | 0.75 |
| **Hands only n (%) | 58 (11.2) | 23 (14.4) | 35 (9.8) | 0.1 | - | - |
| **Feet only n (%) | 46 (8.9) | 22 (13.8) | 24 (6.7) | 0.009 | - | - |
| **Hands and feet n (%) | 44 (8.5) | 22 (13.8) | 22 (6.2) | 0.004 | - | - |
| SHS erosion score (mean ± SD) | 0.8 ± 2 | 1.5 ± 3 | 0.5 ± 1.3 | < 0.001 | - | - |
ACPA = anticyclic citrullinated peptide antibody; CRP = C-reactive protein; ESR = erythrocytic sedimentation rate; HAQ = health assessment questionnaire; LR+ = positive likelihood ratio; LR- = negative likelihood ratio; RA = rheumatoid arthritis; RF = rheumatoid factor; SD = standard deviation; SHS = Sharp/van der Heijde scoring; UA = undifferentiated arthritis.
Morning stiffness score on a 100 mm visual analogue scale.
* P value is calculated in reference to the no-erosion group; ** Defined as a broken cortex in at least 1 joint.