Agreements between local and central readings for various definitions of a positive MRI-SIJ for structural lesions
| MRI central reading (mean of the two central readers) | ||||||
|---|---|---|---|---|---|---|
| Definition 1: ≥1 erosion or ≥1 fatty lesion or ankylosis | Definition 2: ≥1 erosion | Definition 3: ≥2 erosions | ||||
| MRI local reading | PPA (%) | NPA (%) | PPA (%) | NPA (%) | PPA (%) | NPA (%) |
| Definition 1: at least unilateral grade ≥1 | 61.6 | 69.9 | 54.3 | 76.7 | 48.6 | 80.5 |
| κ (95% CI): 0.34 (0.27 to 0.40) | κ (95% CI): 0.31 (0.24 to 0.39) | κ (95% CI): 0.31 (0.24 to 0.39) | ||||
| Definition 2: at least unilateral grade 2 | 53.5 | 69.8 | 54.3 | 79.9 | 49.8 | 85.0 |
| κ (95% CI): 0.29 (0.22 to 0.35) | κ (95% CI): 0.35 (0.27 to 0.43) | κ (95% CI): 0.35 (0.27 to 0.43) | ||||
| Definition 3: bilateral grade 2 | 44.3 | 69.5 | 48.0 | 80.8 | 50.0 | 88.3 |
| κ (95% CI): 0.24 (0.18 to 0.29) | κ (95% CI): 0.31 (0.24 to 0.39) | κ (95% CI): 0.38 (0.30 to 0.47) | ||||
| Definition 4: ≥3 erosions | Definition 5: ≥1 fatty lesion | Definition 6: ≥2 fatty lesions | ||||
| Definition 1 | 38.0 | 80.2 | 55.9 | 79.0 | 52.3 | 81.8 |
| κ (95% CI): 0.24 (0.17 to 0.30) | κ (95% CI): 0.35 (0.28 to 0.43) | κ (95% CI): 0.36 (0.29 to 0.43) | ||||
| Definition 2 | 40.8 | 85.6 | 56.5 | 83.3 | 54.2 | 86.3 |
| κ (95% CI): 0.28 (0.20 to 0.37) | κ (95% CI): 0.40 (0.32 to 0.48) | κ (95% CI): 0.41 (0.33 to 0.49) | ||||
| Definition 3 | 46.4 | 90.1 | 52.1 | 85.1 | 56.9 | 89.9 |
| κ (95% CI): 0.37 (0.28 to 0.46) | κ (95% CI): 0.38 (0.30 to 0.46) | κ (95% CI): 0.47 (0.38 to 0.55) | ||||
| Definition 7: ≥3 fatty lesions | Definition 8: ankylosis | Definition 9: ≥3 erosions and/or fatty lesions | ||||
| Definition 1 | 46.9 | 82.9 | 30.3 | 70.4 | 56.8 | 81.5 |
| κ (95% CI): 0.34 (0.27 to 0.41) | κ (95% CI): 0.02 (-0.05 to 0.10) | κ (95% CI): 0.39 (0.32 to 0.47) | ||||
| Definition 2 | 50.2 | 87.7 | 26.3 | 75.1 | 57.6 | 85.6 |
| κ (95% CI): 0.40 (0.31 to 0.48) | κ (95% CI): 0.01 (-0.06 to 0.09) | κ (95% CI): 0.43 (0.35 to 0.51) | ||||
| Definition 3 | 56.2 | 91.8 | 24.1 | 79.5 | 57.0 | 88.3 |
| κ (95% CI): 0.48 (0.39 to 0.57) | κ (95% CI): 0.04 (-0.04 to 0.12) | κ (95% CI): 0.46 (0.38 to 0.54) | ||||
κ in bold represent κ >0.40.
MRI-SIJ, MRI of the sacroiliac joints; NPA, negative percent agreement; PPA, positive percent agreement.