Frailty Models with Missing Covariates
We present a method for estimating the parameters in random effects models for survival data when covariates are subject to missingness. Our method is more general than the usual frailty model as it accommodates a wide range of distributions for the random effects, which are included as an offset in the linear predictor in a manner analogous to that used in generalized linear mixed models. We propose using a Monte Carlo EM algorithm along with the Gibbs sampler to obtain parameter estimates. This method is useful in reducing the bias that may be incurred using complete-case methods in this setting. The methodology is applied to data from Eastern Cooperative Oncology Group melanoma clinical trials in which observations were believed to be clustered and several tumor characteristics were not always observed.
Document Type: Research Article
Affiliations: Department of Biostatistics, University of North Carolina, 3104-D McGavran-Greenberg Hall, Campus Box 7420, Chapel Hill, North Carolina 27599, U.S.A.
Publication date: 2002-03-01