Document Detail


A varying-coefficient method for analyzing longitudinal clinical trials data with nonignorable dropout.
MedLine Citation:
PMID:  22101223     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Dropout is common in longitudinal clinical trials and when the probability of dropout depends on unobserved outcomes even after conditioning on available data, it is considered missing not at random and therefore nonignorable. To address this problem, mixture models can be used to account for the relationship between a longitudinal outcome and dropout. We propose a Natural Spline Varying-coefficient mixture model (NSV), which is a straightforward extension of the parametric Conditional Linear Model (CLM). We assume that the outcome follows a varying-coefficient model conditional on a continuous dropout distribution. Natural cubic B-splines are used to allow the regression coefficients to semiparametrically depend on dropout and inference is therefore more robust. Additionally, this method is computationally stable and relatively simple to implement. We conduct simulation studies to evaluate performance and compare methodologies in settings where the longitudinal trajectories are linear and dropout time is observed for all individuals. Performance is assessed under conditions where model assumptions are both met and violated. In addition, we compare the NSV to the CLM and a standard random-effects model using an HIV/AIDS clinical trial with probable nonignorable dropout. The simulation studies suggest that the NSV is an improvement over the CLM when dropout has a nonlinear dependence on the outcome.
Authors:
Jeri E Forster; Samantha MaWhinney; Erika L Ball; Diane Fairclough
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Publication Detail:
Type:  Comparative Study; Journal Article; Randomized Controlled Trial; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2011-11-12
Journal Detail:
Title:  Contemporary clinical trials     Volume:  33     ISSN:  1559-2030     ISO Abbreviation:  Contemp Clin Trials     Publication Date:  2012 Mar 
Date Detail:
Created Date:  2012-01-30     Completed Date:  2012-06-26     Revised Date:  2013-06-27    
Medline Journal Info:
Nlm Unique ID:  101242342     Medline TA:  Contemp Clin Trials     Country:  United States    
Other Details:
Languages:  eng     Pagination:  378-85     Citation Subset:  IM    
Copyright Information:
Copyright © 2011 Elsevier Inc. All rights reserved.
Affiliation:
Department of Pediatrics, University of Colorado Denver, Campus Box B119, Aurora, CO 80045, USA.
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MeSH Terms
Descriptor/Qualifier:
Algorithms
Anti-HIV Agents / therapeutic use*
Biometry / methods*
HIV / genetics
HIV Infections / drug therapy*
Humans
Models, Statistical*
Patient Dropouts / statistics & numerical data*
Probability*
RNA, Viral / analysis
Grant Support
ID/Acronym/Agency:
1 R01 DA030495/DA/NIDA NIH HHS; 1 R03 DA026743/DA/NIDA NIH HHS; P30 AI 054907/AI/NIAID NIH HHS; P30 AI054907-02/AI/NIAID NIH HHS; R01 DA030495-01/DA/NIDA NIH HHS; R03 DA026743-01/DA/NIDA NIH HHS
Chemical
Reg. No./Substance:
0/Anti-HIV Agents; 0/RNA, Viral
Comments/Corrections

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