Limits of agreement (LoA)

Limits of agreement estimate the interval within which a proportion of the differences between measurements lie.

The limits of agreement includes both systematic (bias) and random error (precision), and provide a useful measure for comparing the likely differences between individual results measured by two methods. When one of the methods is a reference method, the limits of agreement can be used as a measure of the total error of a measurement procedure (Krouwer, 2002).

Limits of agreement can be derived using parametric method given the assumption of normality of the differences. or using non-parametric percentiles when such assumptions do not hold.