Comparison of MRI-based classification between sacroiliac joint MRI alone and spine MRI alone, and between either SIJ or spine MRI alone with combined sacroiliac joint and spine MRI: Mean number (percentage) of subjects
| Cohort | A (n=62) | B (n=88) | |||||
|---|---|---|---|---|---|---|---|
| Group | nr-axSpA | AS | NSBP | HC | nr-axSpA | AS | NSBP |
| Number of subjects | 19 | 9 | 14 | 20 | 31 | 24 | 33 |
| SIJ MRI vs spine MRI | |||||||
| SIJ+/spine+ | 6.8 (35.5) | 6.5 (72.2) | 0.8 (5.4) | 0.3 (1.3) | 9.0 (29.0) | 17.5 (72.9) | 2.5 (7.6) |
| SIJ+/spine− | 7.8 (40.8) | 2.5 (27.8) | 0.3 (1.8) | 1.3 (6.3) | 5.3 (16.9) | 6.5 (27.1) | 2.8 (8.3) |
| SIJ−/spine+ | 3.0 (15.8) | 0 (0) | 4.0 (28.6) | 5.0 (25.0) | 6.0 (19.4) | 0 (0) | 6.8 (20.5) |
| SIJ−/spine− | 1.5 (7.9) | 0 (0) | 9.0 (64.3) | 13.5 (67.5) | 10.8 (34.7) | 0 (0) | 21.0 (63.6) |
| SIJ+ confid 5–7/Spine+ confid 8–10 | 0.5 (2.6) | 0 (0) | 0.5 (3.6) | 0 (0) | 1.3 (4.0) | 0.5 (2.1) | 0.5 (1.5) |
| SIJ MRI vs combined MRI | |||||||
| SIJ+/Combined+ | 14.0 (73.7) | 9.0 (100.0) | 0.8 (5.4) | 1.5 (7.5) | 13.5 (43.5) | 23.8 (99.0) | 4.3 (12.9) |
| SIJ+/Combined− | 0.5 (2.6) | 0 (0) | 0.3 (1.8) | 0 (0) | 0.8 (2.4) | 0.3 (1.0) | 1.0 (3.0) |
| SIJ−/Combined+ | 3.0 (15.8) | 0 (0) | 3.8 (26.8) | 3.5 (17.5) | 7.5 (24.2) | 0 (0) | 3.8 (11.4) |
| SIJ−/Combined− | 1.5 (7.9) | 0 (0) | 9.3 (66.1) | 15.0 (75.0) | 9.3 (29.8) | 0 (0) | 24.0 (72.7) |
| SIJ+ confid 5–7/Combined+ confid 8–10 | 1.3 (6.6) | 0 (0) | 0.5 (3.6) | 0.3 (1.3) | 2.3 (7.3) | 1.0 (4.2) | 0.8 (2.3) |
| Spine MRI vs combined MRI | |||||||
| Spine+/Combined+ | 9.5 (50.0) | 6.5 (72.2) | 3.0 (21.4) | 2.3 (11.3) | 13.5 (43.5) | 17.3 (71.9) | 4.3 (12.9) |
| Spine+/Combined− | 0.3 (1.3) | 0 (0) | 1.8 (12.5) | 3.0 (15.0) | 1.5 (4.8) | 0.3 (1.0) | 5.0 (15.2) |
| Spine−/Combined+ | 7.5 (39.5) | 2.5 (27.8) | 1.5 (10.7) | 2.8 (13.8) | 7.5 (24.2) | 6.5 (27.1) | 3.8 (11.4) |
| Spine−/Combined− | 1.8 (9.2) | 0 (0) | 7.8 (55.4) | 12.0 (60.0) | 8.5 (27.4) | 0 (0) | 20.0 (60.6) |
| Spine+ confid 5–7/Combined+ confid 8–10 | 2.3 (11.8) | 1.5 (16.7) | 0.8 (5.4) | 0.5 (2.5) | 3.8 (12.1) | 3.3 (13.5) | 1.5 (4.5) |
MRI data are the mean number (percentage) of subjects over four readers.
Confidence range 5–7 reflects a moderate confidence with a MRI-based classification of spondyloarthritis. Confidence range 8–10 indicates a high level of confidence with a MRI-based classification of spondyloarthritis.
AS, ankylosing spondylitis; Confid, confidence; HC, healthy control; nr-axSpA, non-radiographic axial spondyloarthritis; NSBP, non-specific back pain; SIJ, sacroiliac joint.