Sociodemographic data, clinical characteristics, disease activity and disease burden across the three clusters with regard to the location of the enthesitis
| Cluster 1B N=4089 | Cluster 2B N=256 | Cluster 3B N=120 | |
| Rheumatologist’s diagnosis | |||
| Axial spondyloarthritis | 2510 (61.4%) | 164 (64.1%) | 45 (37.5%) |
| Peripheral spondyloarthritis | 392 (9.6%) | 23 (9.0%) | 18 (15.0%) |
| Psoriatic arthritis | 929 (22.7%) | 55 (21.5%) | 49 (40.8%) |
| ReA or IBD-SpA | 157 (3.8%) | 8 (3.1%) | 3 (2.5%) |
| Juv-SpA or others | 101 (2.5%) | 6 (2.3%) | 5 (4.2%) |
| Classification criteria | |||
| ASAS axial criteria | 2683 (65.6%) | 196 (76.6%) | 74 (61.7%) |
| ASAS peripheral ‘strict’ criteria | 492 (12.0%) | 34 (13.3%) | 29 (24.2%) |
| ASAS peripheral ‘non-strict’ criteria | 1176 (28.8%) | 55 (21.5%) | 40 (33.3%) |
| CASPAR criteria | 932 (22.8%) | 57 (22.3%) | 54 (45.0%) |
| Demographic characteristics | |||
| Age | 44.5 (14.0) | 42.8 (12.5) | 45.3 (13.9) |
| Disease duration | 14.3 (11.4) | 14.6 (10.6) | 14.0 (11.6) |
| Sex (male) | 2532 (61.9%) | 144 (56.2%) | 48 (40.0%) |
| Ever smoker | 1752 (42.9%) | 104 (40.6%) | 44 (36.7%) |
| Ever alcohol | 1682 (41.2%) | 93 (36.3%) | 37 (30.8%) |
| Phenotype | |||
| HLA-B27+ | 1932/2885 (66.7%) | 104/169 (61.5%) | 30/66 (45.5%) |
| Axial involvement (ever) | 3125 (76.4%) | 221 (86.3%) | 82 (68.3%) |
| Arthritis (ever) | 2267 (55.4%) | 177 (69.1%) | 97 (80.8%) |
| Dactylitis (ever) | 600 (14.7%) | 57 (22.3%) | 28 (23.3%) |
| Uveitis (ever) | 703 (17.2%) | 48 (18.8%) | 11 (9.2%) |
| Psoriasis (ever) | 1160 (28.4%) | 60 (23.4%) | 58 (48.3%) |
| IBD (ever) | 261 (6.4%) | 15 (5.9%) | 5 (4.2%) |
| Treatment | |||
| csDMARDs (ever) | 2665 (65.2%) | 210 (82.0%) | 112 (93.3%) |
| bDMARDs (ever) | 2408 (58.9%) | 159 (62.1%) | 80 (66.7%) |
| Disease activity and severity | |||
| BASDAI | 3.7 (2.4) | 5.0 (2.6) | 5.3 (2.4) |
| ASDAS-CRP | 2.5 (1.1) | 3.1 (1.2) | 3.1 (1.1) |
| BASFI | 2.9 (2.6) | 4.2 (2.9) | 4.3 (2.8) |
| ASAS-HI | 6.3 (4.5) | 8.9 (4.4) | 10.4 (4.2) |
| Concomitant fibromyalgia | 657/3785 (17.4%) | 73/233 (31.1%) | 45 (41.3%) |
All results are presented as mean and SD and percentages for continuous and categorical variables, respectively.
*Presence of Fibromyalgia defined by the fulfilment of the Fibromyalgia Rapid Screen Tool (FiRST).13
ASAS-HI, ASAS Health Index; ASDAS-CRP, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; IBD, inflammatory bowel disease; Juv-SpA, juvenile SpA; ReA, reactive arthritis.