Table 4.
Clinical characteristics and HLA-B27 test results of patients with nonradiographic axial spondyloarthritis, ankylosing spondylitis, and other inflammatory back pain
| Total (N = 914) | nr-axSpA (n = 266) | AS (n = 491) | Other IBP (n = 157) | p Value | |
|---|---|---|---|---|---|
| HLA-B27 test results (when available) | <0.001 | ||||
| Positive, n (%) | 397 (72.98 %) | 135 (71.43 %) | 250 (82.78 %) | 12 (22.64 %) | |
| Negative, n (%) | 147 (27.02 %) | 54 (28.57 %) | 52 (17.22 %) | 41 (77.36 %) | |
| Years from IBP to SpA diagnosis | 0.747 | ||||
| Number of patients | 179 | 98 | 27 | 54 | |
| Mean ± SD, years | 5.40 ± 7.98 | 5.21 ± 7.69 | 6.48 ± 8.53 | 5.19 ± 8.32 | |
| Family history of SpA | <0.001 | ||||
| Yes, n (%) | 220 (24.07 %) | 70 (26.32 %) | 132 (26.88 %) | 18 (11.46 %) | |
| No, n (%) | 650 (71.12 %) | 180 (67.67 %) | 343 (69.86 %) | 127 (80.89 %) | |
| Results not available, n (%) | 44 (4.81 %) | 16 (6.02 %) | 16 (3.26 %) | 12 (7.64 %) | |
| Family history of SpA (excluding missing) | <0.001 | ||||
| Yes, n (%) | 220 (25.29 %) | 70 (28.00 %) | 132 (27.79 %) | 18 (12.41 %) | |
| No, n (%) | 650 (74.71 %) | 180 (72.00 %) | 343 (72.21 %) | 127 (87.59 %) | |
| NSAID response | 0.125 | ||||
| Positive, n (%) | 657 (71.88 %) | 183 (68.80 %) | 358 (72.91 %) | 116 (73.89 %) | |
| Negative, n (%) | 231 (25.27 %) | 72 (27.07 %) | 125 (25.46 %) | 34 (21.66 %) | |
| Results not available, n (%) | 26 (2.84 %) | 11 (4.14 %) | 8 (1.63 %) | 7 (4.46 %) | |
| Most recent CRP value | 0.146 | ||||
| Number of patients | 767 | 226 | 421 | 120 | |
| Mean ± SD, mg/L | 16.7 ± 26.0 | 15.8 ± 28.2 | 18.2 ± 25.3 | 13.2 ± 23.5 | |
| Most recent CRP level | <0.001 | ||||
| Not elevated (<3.5 mg/L), n (%) | 219 (23.96 %) | 72 (27.07 %) | 96 (19.55 %) | 51 (32.48 %) | |
| Elevated (≥3.5 mg/L), n (%) | 548 (59.96 %) | 154 (57.89 %) | 325 (66.19 %) | 69 (43.95 %) | |
| Results not available, n (%) | 147 (16.08 %) | 40 (15.04 %) | 70 (14.26 %) | 37 (23.57 %) | |
| Most recent CRP level (excluding missing) | <0.001 | ||||
| Not elevated (<3.5 mg/L), n (%) | 219 (28.55 %) | 72 (31.86 %) | 96 (22.80 %) | 51 (42.50 %) | |
| Elevated (≥3.5 mg/L), n (%) | 548 (71.45 %) | 154 (68.14 %) | 325 (77.20 %) | 69 (57.50 %) | |
| Most recent ESR value | 0.009 | ||||
| Number of patients | 846 | 252 | 464 | 130 | |
| Mean ± SD, mm/h | 29.0 ± 23.6 | 26.8 ± 23.9 | 31.2 ± 23.6 | 25.3 ± 22.8 | |
| Most recent ESR level | <0.001 | ||||
| Not elevated (<28 mm/h), n (%) | 482 (52.74 %) | 158 (59.40 %) | 237 (48.27 %) | 87 (55.41 %) | |
| Elevated (≥28 mm/h), n (%) | 364 (39.82 %) | 94 (35.34 %) | 227 (46.23 %) | 43 (27.39 %) | |
| Results not available, n (%) | 68 (7.44 %) | 14 (5.26 %) | 27 (5.50 %) | 27 (17.20 %) | |
| Most recent ESR level (excluding missing) | <0.001 | ||||
| Not elevated (<28 mm/h), n (%) | 482 (56.97 %) | 158 (62.70 %) | 237 (51.08 %) | 87 (66.92 %) | |
| Elevated (≥28 mm/h), n (%) | 364 (43.03 %) | 94 (37.30 %) | 227 (48.92 %) | 43 (33.08 %) |
Abbreviations: AS ankylosing spondylitis, CRP C-reactive protein, ESR erythrocyte sedimentation rate, HLA-B27 human leukocyte antigen B27, IBP inflammatory back pain, nr-axSpA nonradiographic axial spondyloarthritis, NSAID nonsteroidal anti-inflammatory drug, SpA spondyloarthritis
The p values represent the omnibus statistical comparison of percentages (or means) across IBP groups based on the chi-square values