title: A weighted cumulative sum (WCUSUM) to monitor medical outcomes with dependent censoring.
abstract: We develop a weighted cumulative sum (WCUSUM) to evaluate and monitor pre-transplant waitlist mortality of facilities in the context where transplantation is considered to be dependent censoring. Waitlist patients are evaluated multiple times in order to update their current medical condition as reflected in a time-dependent variable called the Model for End-Stage Liver Disease (MELD) score. Higher MELD scores are indicative of higher pre-transplant death risk. Moreover, under the current liver allocation system, patients with higher MELD scores receive higher priority for liver transplantation. To evaluate the waitlist mortality of transplant centers, it is important to take this dependent censoring into consideration. We assume a 'standard' transplant practice through a transplant model and utilize inverse probability censoring weights to construct a WCUSUM. We evaluate the properties of a weighted zero-mean process as the basis of the proposed WCUSUM. We then discuss a resampling technique to obtain control limits. The proposed WCUSUM is illustrated through the analysis of national transplant registry data.
authors.affiliation: Department of Biostatistics, University of Michigan, 1415 Washington Heights, Ann Arbor, MI, U.S.A.
authors.forename: Rena Jie
authors.initials: RJ
authors.lastname: Sun
authors.forename: John D
authors.initials: JD
authors.lastname: Kalbfleisch
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Schaubel
mesh_terms: D056808:Biostatistics; D003198:Computer Simulation; D006801:Humans; D016031:Liver Transplantation / Q000401:mortality* / Q000706:statistics & numerical data; D015233:Models, Statistical; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data; D018579:Patient Selection; D012042:Registries / Q000706:statistics & numerical data; D012720:Severity of Illness Index; D009927:Tissue and Organ Procurement / Q000706:statistics & numerical data; D014481:United States / Q000453:epidemiology; D014850:Waiting Lists / Q000401:mortality*
keywords: control limits; cumulative sum (CUSUM); dependent censoring; failure time data; inverse probability weights; quality control; quality improvement; resampling; risk adjustment