MRI lesions based on sacroiliac joint quadrants affected by BMO or erosion at the group and individual level
| Cohort | A (n=89) | B (n=88) | |||||
|---|---|---|---|---|---|---|---|
| Group | nr-axSpA | AS | NSBP | HC | nr-axSpA | AS | NSBP |
| Number of subjects | 20 | 10 | 39 | 20 | 31 | 24 | 33 |
| SIJ quadrants on group level, median (IQR) | |||||||
| BMO | 15.0 (2.8; 23.5) | 26.5 (10.5; 34.0) | 0 (0; 1.0) | 0 (0; 2.0) | 0 (0; 4.3) | 8.0 (1.0; 20.5) | 0 (0; 2.0) |
| ER | 3.0 (0; 7.3) | 15.0 (8.0; 23.3) | 0 (0; 0) | 0 (0; 0) | 0 (0; 3.0) | 9.0 (2.5; 18.5) | 0 (0; 0) |
| SIJ quadrants on individual level, mean (%) | |||||||
| ≥1 BMO | 16.8 (83.8) | 8.8 (87.5) | 11.0 (28.2) | 7.0 (35.0) | 14.5 (46.8) | 18.5 (77.1) | 10.3 (31.1) |
| ≥2 BMO | 16.0 (80.0) | 8.3 (82.5) | 9.3 (23.7) | 6.0 (30.0) | 13.0 (41.9) | 17.5 (72.9) | 9.0 (27.3) |
| ASAS | 16.0 (80.0) | 8.3 (82.5) | 9.0 (23.1) | 6.0 (30.0) | 13.0 (41.9) | 17.0 (70.8) | 8.8 (26.5) |
| ≥3 BMO | 15.0 (75.0) | 8.0 (80.0) | 4.5 (11.5) | 2.8 (13.8) | 10.5 (33.9) | 15.3 (63.5) | 5.3 (15.9) |
| ≥4 BMO | 14.0 (70.0) | 8.0 (80.0) | 3.0 (7.7) | 2.0 (10.0) | 8.5 (27.4) | 15.0 (62.5) | 4.3 (12.9) |
| ≥5 BMO | 13.3 (66.3) | 8.0 (80.0) | 2.0 (5.1) | 1.3 (6.3) | 7.8 (25.0) | 14.3 (59.4) | 3.0 (9.1) |
| ≥1 ER | 12.8 (63.8) | 9.8 (97.5) | 2.0 (5.1) | 0.8 (3.8) | 10.5 (33.9) | 19.3 (80.2) | 5.3 (15.9) |
| ≥2 ER | 11.5 (57.5) | 9.8 (97.5) | 1.3 (3.2) | 0.5 (2.5) | 9.3 (29.8) | 18.5 (77.1) | 3.3 (9.8) |
| ≥3 ER | 10.8 (53.8) | 9.5 (95.0) | 0.8 (1.9) | 0.5 (2.5) | 8.3 (26.6) | 17.8 (74.0) | 2.5 (7.6) |
| ≥4 ER | 9.3 (46.3) | 9.0 (90.0) | 0.5 (1.3) | 0.5 (2.5) | 6.5 (21.0) | 17.3 (71.9) | 1.5 (4.5) |
| ≥5 ER | 8.0 (40.0) | 8.8 (87.5) | 0.5 (1.3) | 0.5 (2.5) | 6.3 (20.2) | 15.5 (64.6) | 1.5 (4.5) |
| Subjects with ≥1 BMO vs ≥1 ER, mean (%) | |||||||
| BMO+/ER+ | 11.3 (56.3) | 8.8 (87.5) | 0.5 (1.3) | 0.5 (2.5) | 7.0 (22.6) | 16.8 (69.8) | 4.5 (13.6) |
| BMO+/ER− | 5.0 (25.0) | 0 (0) | 10.5 (26.9) | 6.5 (32.5) | 7.5 (24.2) | 1.8 (7.3) | 5.8 (17.4) |
| BMO−/ER+ | 1.5 (7.5) | 1.0 (10.0) | 1.5 (3.8) | 0.3 (1.3) | 3.5 (11.3) | 2.5 (10.4) | 0.8 (2.3) |
| BMO−/ER− | 2.3 (11.3) | 0.3 (2.5) | 26.5 (67.9) | 12.8 (63.8) | 13.0 (41.9) | 3.0 (12.5) | 22.0 (66.7) |
SIJ quadrants at the group level (median/IQR): the median absolute number (IQR) of SIJ quadrants over four readers affected by BMO or erosion per nr-axSpA/AS/NSBP/HC group.
SIJ quadrants on individual level (mean/%): the mean number (percentage) of individual patients and controls over four readers having SIJ quadrants affected by BMO or erosion (stratified from ≥1 to ≥5 affected SIJ quadrants).AS, ankylosing spondylitis; ASAS, Assessment in SpondyloArthritis international Society definition: ≥2 SIJ quadrants with BMO on the same MRI slice or BMO in the same SIJ quadrant on ≥2 consecutive MRI slices; BMO, bone marrow oedema; ER, erosion; HC, healthy control; nr-axSpA, non-radiographic axial spondyloarthritis; NSBP, non-specific back pain; SIJ, sacroiliac joint.