Discordance of joint assessment is dependent on overall number of active joints. Bland-Altman-Plot for patient and biometrician joint counts, plotting the differences of their joint counts (y-axis) against the mean of the joint counts (x-axis). The discordance of assessment increases with higher number of affected joints.
Radner et al. Arthritis Res Ther 2012 14:R61 doi:10.1186/ar3777