Demographic, clinical, laboratory and radiological characteristics of patients and classification criteria at baseline
| Characteristic | All (n=118) | SpA (n=51) | Non-SpA (n=48) | p Value* | Not classified (n=19)* |
|---|---|---|---|---|---|
| Sex ratio, men/women | 0.6 | 0.5 | 0.5 | NS | 1.1 |
| Age at inclusion in years, median (minimum-maximum) | 40.3 (18.2–85.3) | 38.3 (18.5–68.5) | 41.6 (18.2–85.3) | NS | 36.5 (19–58.3) |
| Median (minimum-maximum) disease duration at inclusion, years | 2.2 (0–20.4) | 2.2 (0.2–20.4) | 2.3 (0–20.3) | NS | 1.9 (0.3–19.4) |
| Age at diagnosis in years, median (minimum-maximum) | 41.6 (19.3–85.9) | 39 (19.3–68.8) | 43.5 (20.1–85.9) | NS | NA |
| Primary inclusion criterion, n (%) | |||||
| IBP† | 48 (41) | 23 (45) | 20 (42) | NS | 5 (26) |
| Arthritis/arthralgia† | 38 (32) | 12 (24) | 18 (38) | NS | 8 (42) |
| Enthesitis/dactylitis† | 12 (10) | 4 (8) | 5 (10) | NS | 3 (16) |
| HLAB27+ AAU†‡ | 20 (17) | 13 (25) | 5 (10) | NS | 2 (11) |
| All manifestations, n (%) | |||||
| IBP† | 73 (62) | 36 (71) | 25 (52) | NS | 12 (63) |
| Isolated inflammatory buttock pain† | 19 (16) | 13 (25) | 4 (8) | 0.02 | 2 (11) |
| Arthritis† | 34 (29) | 16 (31) | 12 (25) | NS | 6 (32) |
| Inflammatory arthralgia† | 33 (28) | 19 (37) | 8 (17) | NS | 6 (32) |
| Enthesitis† | 49 (42) | 25 (49) | 18 (37) | NS | 6 (32) |
| Dactylitis† | 5 (4) | 4 (8) | 0 | NS | 1 (5) |
| Psoriasis‡ | 26 (22) | 17 (33) | 8 (17) | NS | 1 (5) |
| IBD‡ | 5 (4) | 4 (8) | 1 (2) | NS | 0 |
| Family history of SpA‡ | 25 (21) | 18 (35) | 5 (10) | 0.001 | 2 (10) |
| Efficacy of NSAIDs†‡ | 71 (60) | 36 (71) | 22 (46) | 0.01 | 13 (68) |
| HLAB27+ AAU†‡ | 20 (17) | 13 (25) | 5 (10) | NS | 2 (11) |
| Radiological and laboratory findings | |||||
| HLA-B27, n positive/n tested (% positive) | 46/116 (40) | 26/51 (51) | 11/47 (23) | 0.005 | 9/18 (50) |
| Pelvic x-rays, n doubtful/n tested (% doubtful) | 22/113 (19) | 12/50 (24) | 8/47 (17) | NS | 2/16 (13) |
| Pelvic CT scan, n positive/n tested (% positive) | 5/23 (22) | 5/19 (26) | 0/7 (0) | NS | 0/2 (0) |
| Pelvic or lumbar MRI, n positive/n tested (% positive) | 17/83 (20) | 14/39 (36) | 3/34 (9) | 0.006 | 0/10 (0) |
| Classification criteria, n (%) | |||||
| Amor criteria | 45 (38) | 31 (61) | 6 (12) | <0.0001 | 8 (42) |
| ESSG criteria | 63 (53) | 40 (78) | 18 (37) | <0.0001 | 5 (26) |
| Berlin criteria, n positive/n tested (% positive)§ | 20/48 (42) | 14/23 (23) | 4 /20 (20) | <0.0001 | 2 (11) |
| Axial ASAS criteria, n positive/n tested (% positive)§ | 21/48 (44) | 15/23 (65) | 4/20 (20) | 0.003 | 2/5 (40) |
| Peripheral ASAS criteria, n positive/n tested (% positive)¶ | 9/33 (27) | 6/12 (50) | 2/15 (13) | 0.04 | 1/6 (17) |
See online supplement for explanation of primary inclusion criterion.
IBP was the primary inclusion criterion for 48 patients and it was a secondary inclusion criterion for 21/38 patients with arthritis, 5/12 patients with enthesitis and 12/20 patients with B27+ uveitis as the primary inclusion criterion.
↵* Comparison between SpA and non-SpA patients was performed with a t test or Kruskall–Wallis test depending on sample size for continuous and ordinal data, and by χ2 test (Fisher exact test, when appropriate) for categorical data.
↵† Manifestations present and recorded at inclusion.
↵‡ Manifestations retrieved from past medical history.
↵§ Both ASAS axial and Berlin criteria were applied to patients for whom a pelvic MRI was available and presenting with IBP at baseline.
↵¶ ASAS peripheral criteria were applied to patients with clinically confirmed peripheral manifestation at baseline.
AAU, acute anterior uveitis; ASAS, Assessment of SpondyloArthritis international Society; ESSG, European Spondylarthropathy Study Group; IBD, inflammatory bowel disease; IBP, inflammatory back pain; NSAIDs, non-steroidal anti-inflammatory drugs; SpA, spondyloarthritis.