title: Monitoring risk-adjusted medical outcomes allowing for changes over time.
abstract: We consider the problem of monitoring and comparing medical outcomes, such as surgical performance, over time. Performance is subject to change due to a variety of reasons including patient heterogeneity, learning, deteriorating skills due to aging, etc. For instance, we expect inexperienced surgeons to improve their skills with practice. We propose a graphical method to monitor surgical performance that incorporates risk adjustment to account for patient heterogeneity. The procedure gives more weight to recent outcomes and down-weights the influence of outcomes further in the past. The chart is clinically interpretable as it plots an estimate of the failure rate for a "standard" patient. The chart also includes a measure of uncertainty in this estimate. We can implement the method using historical data or start from scratch. As the monitoring proceeds, we can base the estimated failure rate on a known risk model or use the observed outcomes to update the risk model as time passes. We illustrate the proposed method with an example from cardiac surgery.
authors.affiliation: Business and Industrial Statistics Research Group, Department of Statistics and Actuarial Sciences, University of Waterloo, Waterloo, Canada N2L 3G1 shsteine@uwaterloo.ca.
authors.forename: Stefan H
authors.initials: SH
authors.lastname: Steiner
authors.affiliation: Business and Industrial Statistics Research Group, Department of Statistics and Actuarial Sciences, University of Waterloo, Waterloo, Canada N2L 3G1.
authors.forename: R Jock
authors.initials: RJ
authors.lastname: Mackay
mesh_terms: D006348:Cardiac Surgical Procedures / Q000401:mortality / Q000592:standards / Q000706:statistics & numerical data*; D006801:Humans; D016013:Likelihood Functions; D010043:Outcome and Process Assessment, Health Care / Q000592:standards / Q000706:statistics & numerical data*; D020379:Risk Adjustment
keywords: Exponentially weighted moving average; Likelihood; Score function; Weighted estimating equation