A Simple Test for Independent Censoring under the Proportional Hazards Model

A simple method for testing the assumption of independent censoring is developed using a Cox proportional hazards regression model with a time-dependent covariate. This method involves further follow-up of a subset of lost-to-follow-up censored subjects. An adjusted estimator of the survivor function is obtained for the dependent censoring model under a proportional hazards alternative. The proposed procedure is applied to an example of a clinical trial for lung cancer and a simulation study is given for investigating the power of the proposed test.