Sociodemographic data, clinical characteristics, disease activity and disease burden across the three clusters with regard to the location of the dactylitis
| Cluster 1C N=4291 | Cluster 2C N=140 | Cluster 3C N=34 | |
| Rheumatologist’s diagnosis | |||
| Axial spondyloarthritis | 2687 (62.6%) | 28 (20.0%) | 4 (11.8%) |
| Peripheral spondyloarthritis | 408 (9.5%) | 15 (10.7%) | 10 (29.4%) |
| Psoriatic arthritis | 923 (21.5%) | 92 (65.7%) | 18 (52.9%) |
| ReA or IBD-SpA | 165 (3.8%) | 2 (1.4%) | 1 (2.9%) |
| Juv-SpA or others | 108 (2.5%) | 3 (2.1%) | 1 (2.9%) |
| Classification criteria | |||
| ASAS axial criteria | 2885 (67.2%) | 56 (40.0%) | 12 (35.3%) |
| ASAS peripheral ‘strict’ criteria | 497 (11.6%) | 46 (32.9%) | 12 (35.3%) |
| ASAS peripheral ‘non-strict’ criteria | 1171 (27.3%) | 82 (58.6%) | 18 (52.9%) |
| CASPAR criteria | 916 (21.3%) | 99 (70.7%) | 28 (82.4%) |
| Demographic characteristics | |||
| Age | 44.4 (13.9) | 45.9 (13.8) | 51.7 (13.9) |
| Disease duration | 14.3 (11.3) | 14.7 (11.7) | 17.7 (11.3) |
| Sex (male) | 2634 (61.4%) | 72 (51.4%) | 18 (52.9%) |
| Ever smoker | 1834/4287 (42.8%) | 51 (36.4%) | 15 (44.1%) |
| Ever alcohol | 1733 (40.4%) | 55 (39.3%) | 24 (70.6%) |
| Phenotype | |||
| HLA-B27+ | 2018/3028 (66.6%) | 42/80 (52.5%) | 6/12 (50.0%) |
| Axial involvement (ever) | 3334 (77.7%) | 76 (54.3%) | 18 (52.9%) |
| Arthritis (ever) | 2370 (55.2%) | 139 (99.3%) | 32 (94.1%) |
| Enthesitis (ever) | 1873 (43.6%) | 93 (66.4%) | 18 (52.9%) |
| Uveitis (ever) | 744 (17.3%) | 13 (9.3%) | 5 (14.7%) |
| Psoriasis (ever) | 1155 (26.9%) | 96 (68.6%) | 27 (79.4%) |
| IBD (ever) | 275 (6.4%) | 4 (2.9%) | 2 (5.9%) |
| Treatment | |||
| csDMARDs (ever) | 2822 (65.8%) | 135 (96.4%) | 30 (88.2%) |
| bDMARDs (ever) | 2527 (58.9%) | 91 (65.0%) | 29 (85.3%) |
| Disease activity and severity | |||
| BASDAI | 3.8 (2.4) | 4.1 (2.6) | 3.9 (2.3) |
| ASDAS-CRP | 2.5 (1.1) | 2.7 (1.3) | 2.4 (1.2) |
| BASFI | 3.0 (2.6) | 3.0 (2.7) | 2.8 (2.8) |
| ASAS-HI | 6.5 (4.6) | 7.7 (5.1) | 7.8 (4.6) |
| Concomitant fibromyalgia* | 736/3966 (18.6%) | 33/130 (25.4%) | 6/31 (19.4%) |
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.