A repeated measures concordance correlation coefficient. Journal   Statistics in medicine. Citation   Stat Med. 26(16):3095-113 Publication date   2007 Jul 20 Authors   King TS Chinchilli VM Carrasco JL Investigators   Vernon M. Chinchilli Tonya S. King MeSH headings   Models, Statistical Phlebotomy Sensitivity and Specificity MeSH qualifiers   statistics & numerical data Abstract   The concordance correlation coefficient is commonly used to assess agreement between two raters or two methods of measuring a response when the data are measured on a continuous scale. However, the situation may arise in which repeated measurements are taken for each rater or method, e.g. longitudinal studies in clinical trials or bioassay data with subsamples. This paper proposes a coefficient for measuring agreement between two raters or two methods of measuring a response in the presence of repeated measurements. We illustrate the methodology with examples comparing (1) 1-hr versus 2-hr blood draws for measuring cortisol in an asthma clinical trial and (2) two measurements of percentage body fat, from skinfold calipers and dual energy X-ray absorptiometry.