Table 3

Agreement by kappa statistics and intraclass correlation coefficients by four readers jointly and for 60 study subjects.

Lesion

Per subject

Ilium R+L

Sacrum R+L


Kappa value (95% CI)

ER

0.72 (0.57 to 0.84)

0.67 (0.53 to 0.79)

0.56 (0.42 to 0.70)

BME

0.61 (0.47 to 0.74)

0.64 (0.50 to 0.76)

0.71 (0.57 to 0.82)

FI

0.55 (0.41 to 0.68)

0.45 (0.32 to 0.58)

0.60 (0.46 to 0.72)

EEa

0.73 (0.63 to 0.84)

0.68 (0.58 to 0.79)

0.45 (0.35 to 0.56)

BFa

0.63 (0.53 to 0.73)

0.60 (0.50 to 0.70)

0.32 (0.22 to 0.42)

ICC(3, 1)/ICC(2, 1)

ER

0.79/0.75

0.78/0.74

0.71/0.67

BME

0.93/0.92

0.88/0.86

0.94/0.93

FI

0.71/0.63

0.54/0.46

0.75/0.70

EEa

0.72/0.71

0.65/0.63

0.55/0.55

BFa

0.55/0.55

0.59/0.59

0.35/0.35


aEE and BF were assessed as score per four joint surfaces irrespective of the number of SIJ MRI slices affected. Kappa values: MRI lesion as binary variable per subject. Intraclass correlation coefficients: MRI lesion as sum score per subject. AS, ankylosing spondylitis; BF, backfill; BME, bone marrow edema; CI, confidence interval; EE, extended erosion; ER, erosion; FI, fat infiltration; ICC(3, 1), intraclass correlation coefficient (3, 1): Readers are considered not representative of a larger population of readers; ICC(2, 1), Intraclass correlation coefficient (2, 1): Readers are considered representative of a larger population of readers.

Weber et al. Arthritis Research & Therapy 2012 14:R124   doi:10.1186/ar3854

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