Clinical characteristics of the rheumatoid arthritis (RA) and non-RA comparator groups used to generate list of differentially expressed genes, which together comprise a training cohort for machine-learning (total n=111) and the independent undifferentiated arthritis (UA) validation cohort (n=62)
| Training cohort | Test cohort | |||
|---|---|---|---|---|
| RA (n=47) | Non-RA (n=64) | p* | UA† (n=62) | |
| Age (years; mean, SD range) | 60 (46–74) | 48 (34–62) | 0.01 | 52 (37–67) |
| % Female | 65 | 61 | NS | 77 |
| % White Caucasian | 96 | 92 | NS | 90 |
| Symptom duration (weeks; median, IQR) | 12 (8–24) | 21 (10.5–52) | 0.026 | 14 (12–26) |
| Tender joint count (median, IQR) | 10 (4–15) | 7 (2–14) | NS | 8 (3–16.5) |
| Swollen joint count (median, IQR) | 6 (2–10) | 0 (0–2) | <0.001 | 1 (0–3) |
| Morning stiffness (hours; median, IQR) | 1 (0.75–2) | 0.75 (0.1–2) | 0.007 | 1 (0.5–2) |
| ESR (s; median, IQR) | 56 (30–78) | 24 (14–52) | <0.001 | 30 (18–60) |
| CRP (g/l; median, IQR) | 17 (9–62) | 5 (2.5–19) | <0.001 | 8.5 (0–17) |
| ACPA+ (number; per cent) | 29 (62) | 0 (0) | <0.001 | 13 (21) |
| RF+ (number; per cent) | 36 (77) | 3 (6) | <0.001 | 20 (32) |
| DAS28 (median) | 5.37 | NA | – | |
| Leiden prediction score (median, IQR) | NA | NA | – | 6.4 (5–7.6) |
| Outcome diagnoses (number, per cent) | ||||
| RA | 47 (100) | 0 (0) | – | 25 (40) |
| Seronegative sponyloarthropathy | – | 22 (34) | – | 8 (13) |
| Self-limiting inflammatory | – | 12 (19) | – | 9 (15) |
| Other inflammatory | – | 3 (5) | – | 2 (3) |
| OA/non-inflammatory | – | 27 (42) | – | 18 (29) |
Values are mean (1 SD range), median (IQR) or % for normally distributed, skewed or dichotomous data, respectively.
↵* Statistical tests for significant difference between RA and non-RA groups; t-test, Mann–Whitney U or Fisher's exact test for normally distributed, skewed or dichotomous data, respectively.
↵† Demographic, clinical and serological parameters are given for UA–RA and UA–non-RA subgroups in online supplementary table S2. ACPA, anti-citrullinated peptide antibodies; CRP, C reactive protein; DAS28, disease activity score (incorporating 28-swollen/tender joint counts); ESR, erythrocyte sedimentation rate; NS, not significant; OA, osteoarthritis; RA, rheumatoid arthritis; RF, rheumatoid factor; UA, undifferentiated arthritis.