A class of repeated measures concordance correlation coefficients.

The repeated measures concordance correlation coefficient was proposed for measuring agreement between two raters or two methods of measuring a response in the presence of repeated measurements (King et al., 2007). This paper proposes a class of repeated measures concordance correlation coefficients that are appropriate for both continuous and categorical data. We illustrate the methodology with examples comparing (1) 1-hour vs. 2-hour blood draws for measuring cortisol in an asthma clinical trial, (2) two measurements of percentage body fat, from skinfold calipers and dual energy x-ray absorptiometry, and (3) two binary measures of quality of health from an asthma clinical trial.