Continuing our CTML Seminar Series is CTML GSR, Kirsten Landsiedel. Her talk, "Improving the Efficiency of Estimators for Survival in Resampling Designs" will take place on April 9th at 12:00PM at Berkeley Way West, 5th Floor, Room 5401. You won't want to miss it!
Survival is a key metric for evaluating current standards of care for individuals living with HIV. In resource-limited settings, high rates of loss to follow-up (LTFU) often result in underestimation of mortality when only observed deaths are considered. Resampling, which tracks a subset of LTFU patients to ascertain their outcomes, mitigates bias and improves survival estimates. However, common estimators for survival in resampling designs—such as weighted Kaplan-Meier (KM)—fail to leverage covariate information collected during repeated clinic visits, even though this information is highly predictive of survival.
We propose a novel Targeted Maximum Likelihood Estimator (TMLE) for survival in resampling designs, which addresses these limitations by leveraging baseline and longitudinal covariates to achieve greater efficiency. We present: (1) a fully efficient TMLE for data from resampling studies with fixed follow-up time for all participants and (2) an inverse probability of censoring weighted (IPCW) TMLE that accounts for varied follow-up times by stratifying on patients with sufficient follow-up to evaluate survival. This IPCW-TMLE can be made highly efficient through nonparametric or targeted estimation of the follow-up censoring mechanism.