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Activity Number:
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274
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Type:
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Contributed
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Date/Time:
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Tuesday, August 5, 2008 : 10:30 AM to 12:20 PM
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Sponsor:
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Biometrics Section
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| Abstract - #302280 |
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Title:
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A Varying-Coefficient Model for the Evaluation of Time-Varying Concomitant Intervention Effects in Longitudinal Studies
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Author(s):
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Colin O. Wu*+ and Xin Tian and Heejung Bang
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Companies:
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National Heart, Lung, and Blood Institute and National Heart, Lung, and Blood Institute and Weill Medical College of Cornell University
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Address:
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2 Rockledge Center, Bethesda, MD, 20892-7913,
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Keywords:
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Change-Point Models ; Concomitant Intervention ; Longitudinal Study ; Polynomial Splines ; Shared Parameter Model ; Varying-Coefficient Model
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Abstract:
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Concomitant interventions are often introduced during a longitudinal clinical trial to patients who respond undesirably to the prespecified treatments. Because the initiation of a concomitant intervention may depend on the patient's general trend of pre-intervention outcomes, regression approaches that treat the presence of the intervention as a time-dependent covariate may lead to biased estimates for the intervention effects. We propose a varying-coefficient mixed-effects model to evaluate the patient's longitudinal outcome trends before and after the patient's starting time of the intervention. Our model leads to less biased estimates of the intervention effects. Nonparametric estimation and inferences of the coefficient curves and intervention effects are developed using B-splines. Our methods are demonstrated through a longitudinal clinical trial in depression and heart disease.
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