Abstract
We propose a simple method for evaluating agreement between methods of measurement when the measured variable is continuous and the data consists of matched repeated observations made with the same method under different conditions. The conditions may represent different time points, raters, laboratories, treatments, etc. Our approach allows the values of the measured variable and the magnitude of disagreement to vary across the conditions. The coefficient of individual agreement (CIA), which is based on the comparison of the between and within-methods mean squared deviation (MSD) is used to quantify the magnitude of agreement between measurement methods. The new approach is illustrated via two examples from studies designed to compare (a) methods of evaluating carotid stenosis and (b) methods of measuring percent body fat.
Highlights
In studies designed to assess the agreement between methods of measurement, multiple observation are often made with each method on the same subject
In this work we focus on an alternative scaled index for assessing agreement, the coefficient of individual agreement (CIA), that may be preferable to the correlation coefficient (CCC) because it does not depend on the between-subject variability, as elaborated by Barnhart et al (2007a,b)
We presented a simple method for assessing agreement between two or more methods of measurement based on repeated measurements matched on a factor whose levels are considered as conditions
Summary
In studies designed to assess the agreement between methods of measurement, multiple observation are often made with each method on the same subject. These observations can be considered as replicated measurements if the observations with the same method on the same subject are conditionally independent and identically distributed In this case it is assumed that the subject’s true value of the measured quantity remains unchanged across the measurements made by the same method. Agreement studies may be designed such that multiple matched observation with two (or more) methods are conducted on each subject under specific ‘conditions’ where the subject’s true value may change across conditions.
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