Demographic and clinical characteristics of two inception cohorts with spondyloarthritis
| Cohort | A (n=89) | B (n=88) | |||||
|---|---|---|---|---|---|---|---|
| Recruitment mode | Suspected axial SpA by practising rheumatologists or PCP | AAU plus past or present back pain | |||||
| Group | nr-axSpA | AS | NSBP | HC | nr-axSpA | AS | NSBP |
| Number of subjects | 20 | 10 | 39 | 20 | 31 | 24 | 33 |
| Male:female (% male) | 11:9 (55.0) | 8:2 (80.0) | 11:28 (28.2) | 7:13 (35.0) | 17:14 (54.8) | 11:13 (45.8) | 17:16 (51.5) |
| Age (years) | 32.2 (27.0; 39.3) | *30.0 (26.5; 36.0) | 32.7 (27.3; 38.8) | 30.6 (27.6; 34.1) | 36.2 (31.1; 43.2) | *41.5 (37.7; 44.8) | 33.6 (27.1; 42.8) |
| Symptom duration (years) | *1.3 (0.7; 2.4) | *3.9 (3.0; 4.8) | NA | NA | *10.0 (5.0; 19.0) | *12.5 (7.8; 21.3) | NA |
| HLA-B27 positive (%) | 12 (60.0) | 9 (90.0) | ND | ND | 24 (80.0)† | 21 (87.5) | 10 (55.6)† |
| BASDAI (NRS) | 4.4 (2.3; 5.4)‡ | 5.4 (4.0; 5.5)‡ | NA | NA | 3.5 (1.6; 5.9) | 2.0 (1.5; 4.9)† | NA |
| BASFI (NRS) | *1.8 (0.7; 4.6)‡ | 2.7 (1.6; 3.1)‡ | NA | NA | *0.8 (0; 2.3) | 0.6 (0.1; 2.9)† | NA |
| CRP (mg/l) | 4.0 (2.3; 6.8)‡ | 5.0 (2.0; 10.0)‡ | ND | ND | 2.7 (0.5; 5.7) | 8.0 (5.3; 14.0)† | 0.9 (0.7; 1.6)† |
Values are the median (IQR) unless otherwise stated.
*P≤0.05 (Fisher's exact test) between cohorts A and B.
†Cohort B: HLA-B27 values are based on 30 patients with nr-axSpA; BASDAI/BASFI and CRP values are based on 22 patients with AS; in patients with NSBP, HLA-B27 and CRP values are based on 18 subjects; the prevalence of HLA-B27 in patients with AAU in general is 50–60%.24
‡Cohort A: CRP values are based on 18 patients, and BASDAI/BASFI values on 19 patients with nr-axSpA, respectively; BASDAI/BASFI and CRP values are based on nine patients with AS.
AAU, acute anterior uveitis; AS, ankylosing spondylitis; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; CRP, C-reactive protein (reference range ≤5 mg/L); HC, healthy control; HLA-B27, human leucocyte antigen B27; NA, not applicable; ND, not done; nr-axSpA, non-radiographic axial spondyloarthritis; NRS, numeric rating scale; NSBP, non-specific back pain; PCP, primary care physician.