A semiparametric pseudo-score method for analysis of two-phase studies with continuous phase-I covariates |
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Authors: | Nilanjan Chatterjee Yi-Hau Chen |
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Institution: | (1) Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Rockville, MD 20852, USA;(2) Institute of Statistical Science, Academia Sinica, Taipei, 11529, Taiwan, ROC |
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Abstract: | Two-phase study designs can reduce cost and other practical burdens associated with large scale epidemiologic studies by limiting
ascertainment of expensive covariates to a smaller but informative sub-sample (phase-II) of the main study (phase-I). During
the analysis of such studies, however, subjects who are selected at phase-I but not at phase-II, remain informative as they
may have partial covariate information. A variety of semi-parametric methods now exist for incorporating such data from phase-I
subjects when the covariate information can be summarized into a finite number of strata. In this article, we consider extending
the pseudo-score approach proposed by Chatterjee et al. (J Am Stat Assoc 98:158–168, 2003) using a kernel smoothing approach
to incorporate information on continuous phase-I covariates. Practical issues and algorithms for implementing the methods
using existing software are discussed. A sandwich-type variance estimator based on the influence function representation of
the pseudo-score function is proposed. Finite sample performance of the methods are studies using simulated data. Advantage
of the proposed smoothing approach over alternative methods that use discretized phase-I covariate information is illustrated
using two-phase data simulated within the National Wilms Tumor Study (NWTS). |
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Keywords: | Case– control sampling Kernel smoothing Locally weighted least square Measurement error Validation design |
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