Table 2

Frequency of MRI lesions recorded by four readers jointly and percentage concordance among six possible reader pairs.

Lesion

Per subject

Ilium R+L

Sacrum R+L

P-value Ilium versus Sacrum


AS patients (number = 30)

Frequency: median (IQR)a

ER

11.4 (9.0)

8.6 (6.9)

2.1 (2.9)

< 0.0001

BME

13.1 (15.1)

6.8 (10.4)

5.1 (7.9)

0.67

FI

10.9 (11.7)

4.5 (5.3)

5.6 (7.0)

0.06

EE

1.1 (1.4)

1.0 (1.0)

0.0 (0.3)

< 0.0001

BF

1.0 (1.3)

0.8 (1.3)

0.0 (0.3)

< 0.0001

% Concordance six RP: total (positive/negative)b

ER

73.9 (56.9/16.9)

80.0 (75.0/5.0)

67.8 (38.9/28.9)

N/A

BME

85.0 (60.4/24.6)

79.7 (60.3/19.4)

90.3 (60.6/29.7)

N/A

FI

69.7 (43.6/26.1)

66.4 (35.3/31.1)

73.1 (51.9/21.1)

N/A

EE

75.7 (19.7/56.0)

65.8 (32.5/33.3)

85.6 (6.9/78.6)

N/A

BF

80.0 (13.8/66.3)

70.3 (24.7/45.6)

89.7 (2.8/86.9)

N/A

Controls (number = 30)

Frequency: median (IQR)a

ER

0 (0.4)

0 (0.3)

0 (0.0)

0.02

BME

0.1 (0.9)

0 (0.4)

0 (0.3)

0.81

FI

0 (2.1)

0 (0.9)

0 (0.2)

0.26

EE

0 (0.0)

0 (0.0)

0 (0.0)

N/A

BF

0 (0.0)

0 (0.0)

0 (0.0)

0.98

% Concordance six RP: total (positive/negative)b

ER

92.1 (0.8/91.3)

87.8 (1.4/86.4)

96.4 (0.3/96.1)

N/A

BME

89.3 (1.9/87.4)

88.6 (2.2/86.4)

90.0 (1.7/88.3)

N/A

FI

83.8 (2.9/80.8)

80.3 (4.7/75.6)

87.2 (1.1/86.1)

N/A

EE

100.0 (0.0/100.0)

100.0 (0.0/100.0)

100.0 (0.0/100.0)

N/A

BF

98.7 (0.2/98.5)

98.1 (0.3/97.8)

99.2 (0.0/99.2)

N/A


aFrequency of lesions: for ER, BME and FI the number of SIJ quadrants affected; for EE and BF the number of joint surfaces affected irrespective of the number of SIJ MRI slices; bpercentage concordance among six possible reader pairs for 60 joint surfaces (Ilium R+L; Sacrum R+L) and for 120 joint surfaces (per subject). AS, ankylosing spondylitis; BF, backfill; BME, bone marrow edema; EE, extended erosion; ER, erosion; FI, fat infiltration; IQR, interquartile range; L, left; N/A, not applicable; R, right; RP, reader pair; % Concordance six RP, percentage concordance among six possible reader pairs (100% = six concordant reader pairs); total = positive and negative concordance.

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

Open Data