Occurrence rate of MRI lesions of the sacroiliac joints and in the spine according to subcategories from the number of participants (‘n’) with available information
| Parameter (n patients with data available) and subcategory | n (%) patients in each subcategory | Sacroiliac joints | Spine | ||
| n (%) quadrants with BME on MRI | n (%) segments with BME on MRI | n (%) segments with FL on MRI | |||
| Age, years (n=793) | <30 | 114 (14.4%) | 24 (2.63%) | 19 (0.72%) | 208 (7.93%) |
| 30–35 | 120 (15.1%) | 20 (2.08%) | 57 (2.07%) | 288 (10.43%) | |
| 35–40 | 198 (25.0%) | 51 (3.22%) | 104 (2.28%) | 499 (10.96%) | |
| 40–45 | 361 (45.5%) | 92 (3.19%) | 182 (2.19%) | 1309 (15.77%) | |
| Sex (n=793) | Male | 392 (49.4%) | 100 (3.19%) | 158 (1.75%) | 1284 (14.24%) |
| Female | 401 (50.6%) | 87 (2.71%) | 204 (2.21%) | 1020 (11.06%) | |
| hsCRP, mg/dL (n=761) | Normal | 708 (93%) | 169 (2.98%) | 337 (2.07%) | 2054 (12.61%) |
| Increased | 53 (7%) | 15 (3.54%) | 18 (1.48%) | 165 (13.54%) | |
| HLA-B27 (n=756) | Negative | 689 (91.1%) | 157 (2.85%) | 307 (1.94%) | 1995 (12.59%) |
| Positive | 67 (8.9%) | 26 (4.85%) | 38 (2.47%) | 195 (12.65%) | |
| BMI category, kg/m2
(n=793) | <25 (under–normal weight) | 357 (45%) | 60 (2.1%) | 159 (1.94%) | 803 (9.78%) |
| 25–30 (overweight) | 287 (36.2%) | 83 (3.61%) | 146 (2.21%) | 918 (13.91%) | |
| >30 (obese) | 149 (18.8%) | 44 (3.69%) | 57 (1.66%) | 583 (17.01%) | |
| Ever smoked (n=792) | Yes | 497 (62.8%) | 126 (3.17%) | 240 (2.1%) | 1499 (13.11%) |
| No | 295 (37.2%) | 61 (2.58%) | 122 (1.8%) | 800 (11.79%) | |
| Back pain (n=793) | NRS=0 | 342 (43.1%) | 63 (2.30%) | 170 (2.16%) | 985 (12.52%) |
| NRS=1–3 | 223 (28.1%) | 69 (3.87%) | 99 (1.93%) | 648 (12.63%) | |
| NRS≥4 | 228 (28.8%) | 55 (3.02%) | 93 (1.77%) | 671 (12.8%) | |
Percentages were calculated on the basis of the numbers of available sites.
BME, bone marrow oedema; BMI, body mass index; FL, fatty lesions; HLA-B27, human leucocyte antigen-B27; hsCRP, high-sensitivity C reactive protein; NRS, numerical rating scale.