Comparison of demographic, clinical and radiographical characteristics between axial PsA subdivided by HLA-B27 status and AS with psoriasis
| Variable | Axial PsA B27 positive N=26 | Axial PsA B27 negative N=60 | P value | AS with psoriasis N=127 | Axial PsA B27 positive versus AS with psoriasis P value | Axial PsA B27 neg versus AS with psoriasis P value |
| Demographic characteristics | ||||||
| Age, mean (SD) | 45.1 (11.6) | 49.7 (12.2) | 0.11 | 49.9 (12.6) | 0.075 | 0.92 |
| Age at diagnosis, mean (SD) | 35.6 (11.1) | 42.6 (13.6) | 0.024 | 37.9 (12.8) | 0.40 | 0.025 |
| Sex (female), n (%) | 11/26 (42) | 25 (43) | 0.93 | 27 (21.3) | 0.024 | 0.002 |
| Disease duration, median (IQR) | 7.0 (2.0–15.0) | 7.0 (2.0–15.0) | 0.66 | 9.0 (5.0–18.0) | 0.36 | 0.025 |
| Diagnostic delay, median (IQR) | 1.0 (0.0, 4.0) | 1.0 (0.0, 4.0) | 0.91 | 3.5 (0.0, 11.0) | 0.081 | 0.047 |
| BMI, mean (SD) | 28.6 (6.3) | 26.5 (5.2) | 0.17 | 27.8 (5.3) | 0.27 | 0.44 |
| Family history of SpA, n (%) | 6/26 (27) | 5/60 (9) | 0.022 | 19/113 (16.8) | 0.16 | 0.18 |
| Clinical characteristics, n (%) | ||||||
| Cervical pain | 3/26 (12) | 6/60 (10) | 0.83 | 21/127 (16.5) | 0.52 | 0.24 |
| Inflammatory back pain | 24/26 (92.3) | 47/60 (78) | 0.27 | 121/127 (95.3) | 0.54 | 0.002 |
| Alternating buttock pain | 12/26 (46) | 20/60 (33) | 0.26 | 79/125 (63.2) | 0.11 | <0.001 |
| Anterior uveitis | 2/26 (8) | 1/60 (2) | 0.16 | 16/125 (12.8) | 0.46 | 0.014 |
| Inflammatory bowel disease | 1/26 (4) | 0/60 (0) | 0.13 | 5/127 (3.9) | 0.98 | 0.12 |
| Dactylitis | 5/26 (19) | 22/60 (37) | 0.11 | 31/126 (24.6) | 0.56 | 0.088 |
| Enthesitis | 10/26 (38) | 20/60 (33) | 0.65 | 49/125 (39.2) | 0.94 | 0.44 |
| Peripheral arthritis | 18/26 (69) | 47/60 (78) | 0.37 | 72/124 (58.1) | 0.29 | 0.007 |
| Nail disease | 9/26 (35) | 27/60 (45) | 0.37 | 32/124 (25.8) | 0.36 | 0.009 |
| Psoriasis before SpA onset | 10/16 (63) | 36/38 (95) | 0.002 | 64/83 (77) | 0.16 | 0.020 |
| Laboratory findings | ||||||
| CRP (mg/L), median (IQR) | 10.5 (17.5) | 9.7 (17.5) | 0.85 | 9.3 (15.9) | 0.73 | 0.87 |
| ESR (mm/hour), median (IQR) | 19.4 (23.5) | 16.5 (16.4) | 0.53 | 19.1 (16.4) | 0.95 | 0.33 |
| Radiographical findings, n (%) | ||||||
| Definite sacroiliitis (BASRI ≥2) | 15/26 (58) | 31/60 (52) | 0.61 | 122/122 (100.0) | <0.001 | <0.001 |
| Isolated spondylitis (no sacroiliitis) | 3/6 (50) | 6/18 (33) | 0.47 | 0 (0) | <0.001 | <0.001 |
| Any radiographical finding, n (%) | 18/25 (72) | 37/56 (66) | 0.60 | 122/122 (100.0) | <0.001 | <0.001 |
| BASRI sacroiliac joint, median (IQR) | 2.0 (1.0–3.0) | 2.0 (0.0–3.0) | 0.55 | 3.0 (2.0–4.0) | <0.001 | <0.001 |
| BASRI lumbar, median (IQR) | 0.0 (0.0–1.0) | 0.0 (0.0–1.0) | 0.55 | 2.0 (1.0–3.0) | <0.001 | <0.001 |
| BASRI cervical, median (IQR) | 0.0 (0.0–0.0) | 0.0 (0.0–1.0) | 0.19 | 1.0 (0.0–3.0) | <0.001 | <0.001 |
| PROs | ||||||
| BASDAI, median (IQR) | 4.6 (2.2–6.4) | 4.4 (2.3–6.4) | 0.91 | 4.1 (2.4–6.4) | 0.92 | 0.99 |
| BASFI, median (IQR) | 2.0 (1.0–4.8) | 2.3 (1.1–5.4) | 0.46 | 3.8 (1.7–6.6) | 0.086 | 0.16 |
| ASDAS-CRP, median (IQR) | 2.6 (2.0–3.2) | 2.3 (1.5–3.5) | 0.60 | 2.7 (1.9–3.5) | 0.77 | 0.27 |
AS, ankylosing spondylitis; ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BASRI, Bath Ankylosing Spondylitis Radiology Index; BMI, body mass index; CRP, C reactive protein; ESR, erythrocyte sedimentation rate; PRO, patient-reported outcome; PsA, psoriatic arthritis.