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Table 6 Inter-observer agreements for MRI changes in the SIJ and global assessment

From: Spondyloarthritis-related and degenerative MRI changes in the axial skeleton - an inter- and intra-observer agreement study

MRI changes Observers Observed agreement (%) Expected agreement (%) Pairwise weighted Kappa (95% CI) Number of SIJ regions
BMO AB 97.77 89.52 .79 (.69–.86) 384
AC 98.09 91.08 .79 (.68–.87) 384
BC 98.70 91.38 .85 (.79–.90) 384
Combined1    .81 (.78–.84) 384
  Intensity BMO 2 AB 85.00 72.22 .46 (.19–.73) 60
AC - - - -
BC - - - -
Combined1    - -
  Depth BMO 2 AB 85.00 53.67 .68 (.49–.87) 60
AC 82.35 50.52 .64 (.43–.85) 51
BC 92.86 53.06 .85 (.71–.99) 56
Combined1    .73 (.63–.82) 65
FMD AB 97.25 83.26 .84 (.77–.89) 384
AC 97.19 87.28 .78 (.69–.85) 384
BC 95.60 84.77 .71 (.60–.80) 384
Combined1    .78 (.74–.81) 384
  Depth FMD 2 AB 84.91 56.14 .66 (.44–.87) 53
AC 78.05 63.65 .40 (.08–.71) 41
BC 72.55 58.94 .33 (.07–.60) 51
Combined1    .52 (.38–.67) 67
Erosions AB 97.77 92.99 .68 (.49–.81) 384
AC 98.32 96.12 .57 (.30–.76) 384
BC 96.90 94.69 .42 (.20–.63) 384
Combined1    .57 (.51–.62) 384
Subchondral sclerosis AB 98.73 96.29 .66 (.40–.81) 384
AC 99.16 97.21 .70 (.37–.87) 384
BC 98.87 97.15 .60 (.28–.81) 384
Combined1    .65 (.61–.70) 384
Ankylosis AB - - - -
AC - - - -
BC 99.28 97.26 .74 (35–.90) 384
Combined1    - -
Global assessment3 AB 94.2 81.31 .69 (.44–.86) 474
AC 90.75 74.95 .59 (.35–.75) 444
BC 89.39 74.64 .58 (.32–.78) 434
  Combined1    .61 (.46–.75) 474
  1. BMO: Bone marrow oedema, FMD: fatty marrow deposition, - Too few positive ratings for one of the observers to be included in the analysis 1 Intraclass correlation coefficient. 2Only observations where both readers agreed on the presence of BMO/FMD were kept in the analysis. 3Assessed on the entire MRI scan. 4Number of patients assessed.