Comparison of clinical presentation between r-axSpA and nr-axSpA: pooled analysis
| Continuous variables | ||||||||
| Variable | N studies | r-axSpA | nr-axSpA | SMD (95% CI) | P value | I2 | ||
| N patients | pooled mean (95% CI) | N patients | pooled mean (95% CI) | |||||
| Age (years) | 42 | 6922 | 38.2 (35.8 to 40.6) | 3691 | 35.9 (34.6 to 37.3) | 0.20 (0.08 to 0.33) | 0.002 | 86.9% |
| Body mass index (kg/m2) | 8 | 1690 | 26.0 (25.0 to 27.0) | 904 | 25.5 (24.6 to 26.4) | 0.12 (−0.06 to 0.31) | 0.182 | 72.8% |
| Age at symptom onset (years) | 10 | 3903 | 26.3 (24.8 to 27.9) | 1573 | 27.8 (26.3 to 29.4) | −0.11 (−0.17 to −0.05) | <0.001 | 39.2% |
| Disease duration (years) | 34 | 5677 | 8.6 (7.4 to 9.8) | 3043 | 5.0 (4.4 to 5.4) | 0.55 (0.45 to 0.66) | <0.001 | 77.9% |
| Time to diagnosis (years) | 5 | 1970 | 6.1 (5.5 to 6.7) | 542 | 4.2 (2.2 to 6.2) | 0.31 (0.11 to 0.51) | 0.002 | 69.8% |
| SPARCC total SIJ (0 to 72) | 3 | 272 | 7.7 (5.4 to 10.1) | 236 | 7.2 (5.9 to 8.6) | 0.31 (−0.34 to 0.96) | 0.344 | 90.8% |
| Berlin activity score MRI-spine | 2 | 194 | 5.5 (1.6 to 9.4) | 161 | 2.9 (−0.2 to 5.9) | 1.87 (−0.55 to 4.28) | 0.129 | 97.8% |
| mSASSS | 8 | 693 | 8.1 (5.3 to 10.9) | 664 | 2.7 (1.7 to 3.6) | 0.52 (0.41 to 0.63) | <0.001 | 0.0% |
| Binary variables | ||||||||
| Variable | N studies | r-axSpA | nr-axSpA | RR (95% CI) | P value | I2 | ||
| N patients | Pooled percentage (95% CI) | N patients | Pooled percentage (95% CI) | |||||
| Sex (male) | 43 | 8423 | 69.6 (66.2 to 72.7) | 4092 | 53.6 (49.0 to 58.1) | 1.30 (1.18 to 1.43) | <0.001 | 88.3% |
| Ethnicity (Caucasian) | 5 | 1003 | 83.8 (71.1 to 91.6) | 569 | 84.2 (63.2 to 94.3) | 1.02 (0.91 to 1.15) | 0.689 | 77.9% |
| Smoker (ever) | 11 | 3232 | 37.7 (26.9 to 50.0) | 1412 | 31.1 (21.6 to 42.6) | 1.18 (1.09 to 1.28) | <0.001 | 0.0% |
| HLA-B27 positive | 37 | 7273 | 76.7 (71.7 to 81.1) | 3797 | 72.0 (66.8 to 76.7) | 1.04 (0.98 to 1.11) | 0.168 | 81.6% |
| Inflammatory back pain | 6 | 1032 | 86.1 (76.4 to 92.2) | 1156 | 87.8 (71.5 to 95.4) | 1.00 (0.97 to 1.04) | 0.895 | 7.0% |
| Good NSAIDs response | 7 | 1720 | 68.5 (56.0 to 78.8) | 1463 | 61.7 (53.3 to 69.4) | 1.09 (0.95 to 1.26) | 0.200 | 79.5% |
| Family history of SpA | 16 | 3112 | 23.1 (17.1 to 30.4) | 2253 | 25.8 (20.3 to 32.3) | 0.97 (0.88 to 1.05) | 0.447 | 41.4% |
| Peripheral arthritis | 21 | 4824 | 32.8 (27.6 to 38.5) | 2717 | 35.2 (29.0 to 41.9) | 0.87 (0.81 to 0.93) | <0.001 | 45.2% |
| Dactylitis | 12 | 2634 | 5.6 (3.9 to 7.9) | 1725 | 7.6 (5.5 to 10.5) | 0.64 (0.50 to 0.82) | <0.001 | 36.8% |
| Heel enthesitis | 3 | 204 | 21.1 (15.1 to 28.5) | 142 | 26.6 (23.1 to 30.6) | 0.81 (0.53 to 1.24) | 0.343 | 77.0% |
| Any enthesitis | 18 | 4239 | 23.0 (14.0 to 35.4) | 2203 | 30.1 (22.0 to 39.7) | 0.84 (0.74 to 0.96) | 0.009 | 52.7% |
| Uveitis | 25 | 6821 | 18.0 (13.4 to 23.8) | 3268 | 14.3 (12.0 to 16.9) | 1.31 (1.05 to 1.62) | 0.015 | 72.1% |
| Psoriasis | 22 | 5844 | 8.5 (5.6 to 12.8) | 2972 | 9.3 (7.4 to 11.7) | 0.99 (0.85 to 1.15) | 0.891 | 32.7% |
| IBD | 20 | 6284 | 6.5 (5.2 to 8.2) | 2868 | 5.63 (4.01 to 7.86) | 1.05 (0.86 to 1.27) | 0.643 | 0.0% |
| Patients with positive MRI-SIJ ASAS definition | 3 | 503 | 45.7 (18.7 to 75.6) | 400 | 71.5 (66.9 to 75.8) | 0.67 (0.29 to 1.11) | 0.099 | 95.6% |
| Patients with erosion MRI-SIJ | 3 | 141 | 70.8 (41.8 to 89.1) | 131 | 40.9 (20.0 to 67.3) | 1.76 (1.05 to 2.97) | 0.032 | 80.1% |
| Patients with fatty lesions at MRI-SIJ | 3 | 102 | 79.4 (56.1 to 92.1) | 95 | 51.5 (28.4 to 74.0) | 1.41 (1.17 to 1.70) | <0.001 | 32.4% |
| Patients with at least one syndesmophyte | 4 | 423 | 26.4 (14.2 to 43.6) | 239 | 9.7 (4.4 to 20.0) | 2.67 (1.71 to 4.16) | <0.001 | 0.0% |
IBD, inflammatory bowel disease; MRI-SIJ, MRI of the sacroiliac joints; nr-axSpA, non-radiographic axial Spondyloarthritis; NSAIDs, non-steroidal anti-inflammatory drugs; r-axSpA, radiographic axial Spondyloarthritis; RR, relative risk; SMD, standardised means difference; SPARCC, Spondyloarthritis Research Consortium of Canada.