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 (IPCW) to construct a weighted CUSUM. We evaluate the properties of a weighted zero-mean process as the basis of the proposed weighted CUSUM. We then discuss a resampling technique to obtain control limits. The proposed WCUSUM is illustrated through the analysis of national transplant registry data.

Risk‐adjusted monitoring of time to event in the presence of long‐term survivors

“…Phinikettos and Gandy (2014) studied a nonparametric method for monitoring time-to-event data. Sun, Kalbfleisch and Schaubel (2014) developed a weighted cumulative sum to monitor medical outcomes with dependent censoring and Zhang et al (2016) investigate the effect of estimation error on the performance of risk-adjusted survival time CUSUM.…”