Exploratory analysis of longitudinal trials with staggered intervention times

Longitudinal trials involving surgical interventions commonly have subject-specific intervention times, due to constraints on the availability of surgeons and operating theatres. Moreover, the intervention often effects a discontinuous change in the mean response. We propose a nonparametric estimato...

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Bibliographic Details
Published inBiostatistics (Oxford, England) Vol. 6; no. 3; pp. 479 - 485
Main Authors Sousa, Inês, Chetwynd, Amanda G., Diggle, Peter J.
Format Journal Article
LanguageEnglish
Published England Oxford Publishing Limited (England) 01.07.2005
Subjects
Algorithms
Biometry
Clinical Trials as Topic - statistics & numerical data
Emphysema - physiopathology
Emphysema - surgery
Forced Expiratory Volume
Humans
Longitudinal Studies
Statistics, Nonparametric
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Summary:Longitudinal trials involving surgical interventions commonly have subject-specific intervention times, due to constraints on the availability of surgeons and operating theatres. Moreover, the intervention often effects a discontinuous change in the mean response. We propose a nonparametric estimator for the mean response profile of longitudinal data with staggered intervention times and a discontinuity at the times of intervention, as an exploratory tool to assist the formulation of a suitable parametric model. We use an adaptation of the standard generalized additive model algorithm for estimation, with smoothing constants chosen by a cross-validation criterion. We illustrate the method using longitudinal data from a trial to assess the effect of lung resection surgery in the treatment of emphysema patients.
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ISSN:1465-4644
1468-4357
DOI:10.1093/biostatistics/kxi023