Mixed model analysis of censored longitudinal data with flexible random-effects density.

Journal Article

Mixed models are commonly used to represent longitudinal or repeated measures data. An additional complication arises when the response is censored, for example, due to limits of quantification of the assay used. While Gaussian random effects are routinely assumed, little work has characterized the consequences of misspecifying the random-effects distribution nor has a more flexible distribution been studied for censored longitudinal data. We show that, in general, maximum likelihood estimators will not be consistent when the random-effects density is misspecified, and the effect of misspecification is likely to be greatest when the true random-effects density deviates substantially from normality and the number of noncensored observations on each subject is small. We develop a mixed model framework for censored longitudinal data in which the random effects are represented by the flexible seminonparametric density and show how to obtain estimates in SAS procedure NLMIXED. Simulations show that this approach can lead to reduction in bias and increase in efficiency relative to assuming Gaussian random effects. The methods are demonstrated on data from a study of hepatitis C virus.

Full Text

Duke Authors

Cited Authors

  • Vock, DM; Davidian, M; Tsiatis, AA; Muir, AJ

Published Date

  • January 2012

Published In

Volume / Issue

  • 13 / 1

Start / End Page

  • 61 - 73

PubMed ID

  • 21914727

Electronic International Standard Serial Number (EISSN)

  • 1468-4357

Digital Object Identifier (DOI)

  • 10.1093/biostatistics/kxr026

Language

  • eng

Conference Location

  • England