Table 2 Agreement between indices in the SpA population, axSpA, pSpA and PsA

LEI vs. SPARCC vs. MASES vs. MEI

Fleiss’ kappa:

0.705

(CI: 0.69–0.71; p value: 0.001)

0.663

(CI: 0.64–0.67; p value: 0.001)

0.83

(CI: 0.79–0.86; p value: 0.001)

0.74

(CI: 0.71–0.76; p value: 0.001)

LEI vs. SPARCC

Agreement:

96.4%

97.2%

96.1%

94.5%

Cohen’s kappa:

0.79

(CI: 0.76–0.82; p value: 0.001)

0.80

(CI: 0.76–0.85; p value: 0.001)

0.84

(CI: 0.76–0.91; p value: 0.001)

0.74

(CI: 0.68–0.81; p value: 0.001)

MASES vs. SPARCC

Agreement:

92.0%

91.3%

94.9%

92.6%

Cohen’s kappa:

0.62

(CI: 0.58–0.65; p value: 0.001)

0.56

(CI: 0.51–0.61; p value: 0.001)

0.80

(CI: 0.71–0.88; p value: 0.001)

0.67

(CI: 0.6–0.74; p value: 0.001)

MEI vs. SPARCC

Agreement:

93.2%

91.7%

97.2%

95.4%

Cohen’s kappa:

0.71

(CI: 0.68–0.74; p value: 0.001)

0.62

(CI: 0.58–0.67; p value: 0.001)

0.90

(CI: 0.84–0.96; p value: 0.001)

0.83

(CI: 0.78–0.87; p value: 0.001)

MASES vs. LEI

Agreement:

92.9%

91.6%

96.1%

95.1%

Cohen’s kappa:

0.63

(CI: 0.59–0.67; p value: 0.001)

0.55

(CI: 0.5–0.6; p value: 0.001)

0.83

(CI: 0.75–0.91; p value: 0.001)

0.75

(CI: 0.68–0.81; p value: 0.001)

MEI vs. LEI

Agreement:

91.4%

90.4%

94.2%

92.7%

Cohen’s kappa:

0.61

(CI: 0.58–0.65; p value: 0.001)

0.54

(CI: 0.49–0.59; p value: 0.001)

0.78

(CI: 0.69–0.86; p value: 0.001)

0.70

(0.64–0.76; p value: 0.001)

MEI vs. MASES

Agreement:

96.3%

97.3%

95.8%

93.8%

Cohen’s kappa:

0.86

(CI: 0.83–0.88; p value: 0.001)

0.90

(CI: 0.87–0.92; p value: 0.001)

0.85

(CI: 0.78–0.91; p value: 0.001)

0.75

(CI: 0.70–0.81; p value: 0.001)