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

Publication ,  Journal Article
Vock, DM; Davidian, M; Tsiatis, AA; Muir, AJ
Published in: Biostatistics
January 2012

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.

Duke Scholars

Published In

Biostatistics

DOI

EISSN

1468-4357

Publication Date

January 2012

Volume

13

Issue

1

Start / End Page

61 / 73

Location

England

Related Subject Headings

  • Viral Load
  • Statistics, Nonparametric
  • Statistics & Probability
  • Models, Statistical
  • Longitudinal Studies
  • Linear Models
  • Interferon-alpha
  • Humans
  • Hepatitis C
  • Data Interpretation, Statistical
 

Citation

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Vock, D. M., Davidian, M., Tsiatis, A. A., & Muir, A. J. (2012). Mixed model analysis of censored longitudinal data with flexible random-effects density. Biostatistics, 13(1), 61–73. https://doi.org/10.1093/biostatistics/kxr026
Vock, David M., Marie Davidian, Anastasios A. Tsiatis, and Andrew J. Muir. “Mixed model analysis of censored longitudinal data with flexible random-effects density.Biostatistics 13, no. 1 (January 2012): 61–73. https://doi.org/10.1093/biostatistics/kxr026.
Vock DM, Davidian M, Tsiatis AA, Muir AJ. Mixed model analysis of censored longitudinal data with flexible random-effects density. Biostatistics. 2012 Jan;13(1):61–73.
Vock, David M., et al. “Mixed model analysis of censored longitudinal data with flexible random-effects density.Biostatistics, vol. 13, no. 1, Jan. 2012, pp. 61–73. Pubmed, doi:10.1093/biostatistics/kxr026.
Vock DM, Davidian M, Tsiatis AA, Muir AJ. Mixed model analysis of censored longitudinal data with flexible random-effects density. Biostatistics. 2012 Jan;13(1):61–73.
Journal cover image

Published In

Biostatistics

DOI

EISSN

1468-4357

Publication Date

January 2012

Volume

13

Issue

1

Start / End Page

61 / 73

Location

England

Related Subject Headings

  • Viral Load
  • Statistics, Nonparametric
  • Statistics & Probability
  • Models, Statistical
  • Longitudinal Studies
  • Linear Models
  • Interferon-alpha
  • Humans
  • Hepatitis C
  • Data Interpretation, Statistical