Agreement between various definitions of a positive MRI-SIJ for structural lesions (local reading) and radiographic sacroiliitis
| X-ray local reading | X-ray central reading (2/3) | |||||||
|---|---|---|---|---|---|---|---|---|
| Definition 1: at least unilateral ‘DESIR grade’ 2 | Definition 2: at least bilateral ‘DESIR grade’ 2 or unilateral ‘DESIR grade’ 3 | Definition 3: bilateral ‘DESIR grade’ 3 | bilateral ‘mNY grade ≥2’ or at least unilateral ‘mNY grade≥3’ | |||||
| MRI local reading | PPA (%) | NPA (%) | PPA (%) | NPA (%) | PPA (%) | NPA (%) | PPA (%) | NPA (%) |
| Definition 1: at least unilateral grade ≥1 | 63.9 | 83.5 | 51.9 | 83.3 | 2.6 | 78.5 | 56.0 | 82.6 |
| κ (95% CI): 0.48 (0.41 to 0.55) Se=73.9%. Sp=78.6% | κ (95% CI): 0.38 (0.31 to 0.45) Se=83.7%. Sp=73.6% | κ (95% CI): 0.01 (−0.01 to 0.03) Se=75.0%. Sp=64.7% | κ (95% CI): 0.40 (0.33 to 0.47) Se=75.2%. Sp=75.0% | |||||
| Definition 2: at least unilateral grade 2 | 66.9 | 87.9 | 56.7 | 88.4 | 3.4 | 85.0 | 60.4 | 87.7 |
| κ (95% CI): 0.55 (0.48 to 0.62) Se=65.9%. Sp=88.4% | κ (95% CI):0.46 (0.38 to 0.54) Se=75.0%. Sp=82.9% | κ (95% CI): 0.02 (−0.01 to 0.05) Se=75.0%. Sp=74.0% | κ (95% CI): 0.48 (0.40 to 0.56) Se=67.9%. Sp=84.8% | |||||
| Definition 3: bilateral grade 2 | 59.0 | 87.9 | 61.9 | 92.1 | 4.9 | 90.0 | 60.9 | 90.4 |
| κ (95% CI): 0.48 (0.40 to 0.55) Se=49.4%. Sp=93.2% | κ (95% CI):0.54 (0.45 to 0.63) Se=66.3%. Sp=90.8% | κ (95% CI): 0.04 (−0.01 to 0.08) Se=75.0%. Sp=82.0% | κ (95% CI): 0.51 (0.40 to 0.60) Se=56.9%. Sp=92.0% | |||||
κ in bold represent κ >0.40.
MRI-SIJ, MRI of the sacroiliac joints; NPA, negative percent agreement; PPA, positive percent agreement; Se, sensitivity; Sp, specificity.