Question 6: What is meant by ‘limits of agreement’?
The limits of agreement are the range of values which we expect to include 95% of differences between measurements by the two methods.
They are calculated from the differences between the measurements by the two methods, here capillary and laboratory glucose. If we estimate the mean and standard deviation of these differences, the limits of agreement are found by the mean difference minus 1.96 standard deviations to the mean difference plus 1.96 standard deviations.
The limits of agreement provide a measure of the agreement between the two methods of measurement, in the same units as the measurement. We can decide for any given purpose whether the two methods agree sufficiently closely.
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Last updated: 1 March, 2007.