Difference in characteristics of non-radiographic axial SpA vs radiographic axial SpA within Asia
| Variables | nr-axSpA | r-axSpA | P value |
| n | 112 | 668 | |
| Age at disease diagnosis, years | 27.2 (21.1, 39.6) | 26.9 (21.7, 35.6) | 0.79 |
| Age at disease onset, years | 22.8 (18.5, 31.0) | 22.7 (18.3, 29.3) | 0.41 |
| Age at enrolment, years | 33.9 (24.9, 44.0) | 34.9 (26.8, 44.0) | 0.21 |
| Diagnostic delay*, years | 1.9 (0.27, 5.56) | 2.8 (0.50, 7.34) | 0.14 |
| Male (%) | 85 (75.9) | 533 (79.8) | 0.42 |
| Body mass index, kg/m2 | 23.5 (20.7, 26.6) | 22.9 (20.4, 25.7) | 0.15 |
| Smoking status | |||
| Never (%) | 67 (59.8) | 357 (53.4) | 0.25 |
| Past (%) | 17 (15.2) | 124 (18.6) | 0.47 |
| Current (%) | 28 (25.0) | 187 (28.0) | 0.59 |
| Family history of SpA (%) | 36 (32.1) | 228 (34.1) | 0.76 |
| Meeting ASAS axial SpA criteria | |||
| Imaging arm only (%) | 19 (17.0) | 147 (22.0) | 0.28 |
| Clinical arm only (%) | 63 (56.2) | 0 (0.0) | <0.001 |
| Both (%) | 30 (26.8) | 521 (78.0) | <0.001 |
| MRI tested (%) | 73 (65.2) | 249 (37.3) | <0.001 |
| Sacroiliitis among MRI tested (%) | 49 (67.1) | 193 (77.5) | 0.10 |
| HLA B27 measured (%) | 106 (94.6) | 596 (89.2) | 0.11 |
| HLA B27 positivity among measured (%) | 96 (90.6) | 551 (92.4) | 0.64 |
| Inflammatory back pain (%) | 107 (95.5) | 650 (97.3) | 0.36 |
| Arthritis, enthesitis, or dactylitis (%) | 60 (53.6) | 336 (50.3) | 0.59 |
| Peripheral arthritis (%) | 53 (47.3) | 277 (41.5) | 0.29 |
| Heel enthesitis (%) | 33 (29.5) | 159 (23.8) | 0.24 |
| Peripheral enthesitis (%) | 38 (33.9) | 182 (27.2) | 0.18 |
| Dactylitis (%) | 2 (1.8) | 35 (5.2) | 0.18 |
| Psoriasis (%) | 12 (10.7) | 34 (5.1) | 0.03 |
| CASPAR criteria (%) | 6 (5.4) | 12 (1.8) | 0.03 |
| Uveitis (%) | 20 (17.9) | 149 (22.3) | 0.35 |
| Inflammatory bowel disease (%) | 5 (4.5) | 12 (1.8) | 0.08 |
| Erythrocyte sedimentation rate, mm/hour | 10.0 (5.0, 19.0) | 13.0 (6.0, 28.5) | 0.004 |
| C reactive protein (CRP) level, mg/dL | 0.50 (0.30, 1.33) | 0.70 (0.30, 3.00) | 0.02 |
| Elevated CRP (%) | 37 (33.0) | 393 (58.8) | <0.001 |
| Physician global assessment (0–10) | 2.0 (1.0, 5.0) | 3.0 (2.0, 5.0) | 0.03 |
| Patient global assessment (0–10) | 3.0 (1.0, 6.0) | 4.0 (2.0, 6.0) | 0.048 |
| ASDAS-CRP | 1.40 (0.95, 2.08) | 1.79 (1.04, 2.66) | 0.006 |
| BASDAI | 2.8 (1.5, 4.2) | 3.0 (1.7, 4.8) | 0.22 |
| BASFI | 0.8 (0.1, 2.7) | 1.2 (0.2, 3.1) | 0.09 |
| Presence of bamboo spine (%) | 0 (0.0) | 99 (14.8) | <0.001 |
| History of SpA-related surgeries (%) | 0 (0.0) | 36 (5.4) | 0.02 |
| Treatment | |||
| NSAIDs use since onset (%) | 103 (92.0) | 586 (87.7) | 0.26 |
| Good response to NSAIDs (%) | 80 (71.4) | 430 (64.4) | 0.18 |
| Current glucocorticoid use (%) | 10 (8.9) | 65 (9.7) | 0.93 |
| Conventional synthetic DMARDs use (%) | 60 (53.6) | 328 (49.1) | 0.44 |
| Methotrexate use (%) | 18 (16.1) | 90 (13.5) | 0.56 |
| Sulfasalazine use (%) | 51 (45.5) | 296 (44.3) | 0.89 |
| Biological DMARDs (TNF antagonists) use (%) | 27 (24.1) | 197 (29.5) | 0.29 |
| Comorbidities | |||
| Obesity (%) | 24 (21.4) | 107 (16.1) | 0.21 |
| Hypertension (%) | 15 (13.4) | 96 (14.4) | 0.90 |
| Diabetes mellitus (%) | 2 (1.8) | 22 (3.3) | 0.56 |
| Dyslipidaemia (%) | 11 (9.8) | 66 (9.9) | 1 |
| Ischaemic heart disease or stroke (%) | 1 (0.9) | 8 (1.2) | 1 |
| Vertebral or fragility fractures (%) | 2 (1.8) | 22 (3.3) | 0.56 |
Values are expressed as n (%) or median (IQR) unless otherwise indicated.
*Diagnostic delay: the difference between the date of the diagnosis and the date of the first symptom.
ASAS, Assessment of SpondyloArthritis international Society; ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; CASPAR, ClASsification for Psoriatic ARthritis; DMARD, disease-modifying antirheumatic drug; HLA, human leucocyte antigens; nr-axSpA, non-radiographic axial spondyloarthritis; NSAID, non-steroidal anti-inflammatory drug; r-axSpA, radiographic axial spondyloarthritis; SpA, spondyloarthritis; TNF, Tumor Necrosis Factor.