title: A repeated measures concordance correlation coefficient.
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.
authors.affiliation: Division of Biostatistics, Department of Health Evaluation Sciences, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA. tking@psu.edu
authors.forename: Tonya S
authors.initials: TS
authors.lastname: King
authors.forename: Vernon M
authors.initials: VM
authors.lastname: Chinchilli
authors.forename: Josep L
authors.initials: JL
authors.lastname: Carrasco
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue; D001681:Biological Assay; D002986:Clinical Trials as Topic; D006854:Hydrocortisone / Q000032:analysis / Q000097:blood; D015233:Models, Statistical; D018962:Phlebotomy / Q000706:statistics & numerical data*; D015983:Selection Bias; D012680:Sensitivity and Specificity; D013030:Spain
chemical_list: D006854:Hydrocortisone