Keywords: agreement; reliability; coverage probability; measurement error; area under the curve
There has been substantial statistical literature in the last several decades on assessing agreement, and coverage probability approach was selected as a preferred index for assessing and improving measurement agreement in a core laboratory setting. With this approach, a satisfactory agreement is based on pre-specified high satisfactory coverage probability (e.g., 95%), given one pre-specified acceptable difference. In practice, we may want to have quality control on more than one pre-specified differences, or we may simply want to summarize the agreement based on differences up to a maximum acceptable difference. We propose to assess agreement via the coverage probability curve that provides a full spectrum of measurement error at various differences/disagreement. Relative area under the coverage probability curve is proposed for the summary of overall agreement, and this new summary index can be used for comparison of different intra-methods or inter-methods/labs/observers’ agreement. Simulation studies and a blood pressure example are used for illustration of the methodology.