Mean number (percentage) of subjects with a positive sacroiliac joint MRI, positive spine MRI and positive combined MRI, compared with clinical classification as gold standard
| 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 |
| MRI positivity vs clinical classification | |||||||
| SIJ MRI + with confidence range 5–10 | 14.5 (76.3) | 9.0 (100.0) | 1.0 (7.1) | 1.5 (7.5) | 14.3 (46.0) | 24.0 (100.0) | 5.3 (15.9) |
| SIJ MRI + with confidence range 8–10 | 12.3 (64.5) | 8.8 (97.2) | 0 (0) | 0.5 (2.5) | 10.5 (33.9) | 23.0 (95.8) | 2.8 (8.3) |
| Spine MRI + with confidence range 5–10 | 9.8 (51.3) | 6.5 (72.2) | 4.8 (33.9) | 5.3 (26.3) | 15.0 (48.4) | 17.5 (72.9) | 9.3 (28.0) |
| Spine MRI + with confidence range 8–10 | 6.8 (35.5) | 5.0 (55.6) | 2.0 (14.3) | 1.5 (7.5) | 9.8 (31.5) | 15.0 (62.5) | 3.5 (10.6) |
| Spine MRI + showing ≥3 CIL* | 8.3 (43.4) | 5.5 (61.1) | 3.5 (25.0) | 3.5 (17.5) | 7.8 (25.0) | 10.3 (42.7) | 3.5 (10.6) |
| Spine MRI + showing ≥5 CFL* | 6.0 (31.6) | 4.3 (47.2) | 4.5 (32.1) | 4.8 (23.8) | 13.5 (43.5) | 13.0 (54.2) | 8.0 (24.2) |
| Combined MRI + with confidence range 5–10 | 17.0 (89.5) | 9.0 (100.0) | 4.5 (32.1) | 5.0 (25.0) | 21.0 (67.7) | 23.8 (99.0) | 8.0 (24.2) |
| Combined MRI + with confidence range 8–10 | 15.3 (80.3) | 8.8 (97.2) | 2.0 (14.3) | 2.8 (13.8) | 15.5 (50.0) | 23.0 (95.8) | 5.0 (15.2) |
MRI data are the mean number (percentage) of subjects over four readers.
Confidence range 5–10 reflects a moderate to high level of 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.
*CIL/CFL on ≥1 spinal MRI slices.
AS, ankylosing spondylitis; CIL, corner inflammatory lesion (in central spinal MRI slices); CFL, corner fatty lesion (in central spinal MRI slices); HC, healthy control; nr-axSpA, non-radiographic axial spondyloarthritis; NSBP, non-specific back pain; SIJ, sacroiliac joint.