Table 1.

Observer variation between three readers for quantification of disease extent, determination of zonal distribution, and scoring of individual radiographic patterns

Chest radiographic parameter	Kappa coefficient (weighted, Kω / unweighted, K)
Overall extent of disease
Observer 1 versus 2	Kω = 0.88
Observer 1 versus 3	Kω = 0.87
Observer 2 versus 3	Kω = 0.91
Zonal disease distribution
Upper zone	K = 0.80
Mid zone	K = 0.57
Lower zone	K = 0.69
Extent of radiographic pattern
Consolidation	K = 0.70
Reticular pattern	N/A
Non-cavitating nodules	Kω = 0.26
Cavitating nodules	N/A
Ring/tramline opacities	K = 0.51
Ground-glass opacities	N/A
Masses	N/A