Exposure assessment using biologic specimens is important for epidemiology but may become impracticable if assays are expensive, specimen volumes are marginally adequate, or analyte levels fall below the limit of detection. Pooled exposure assessment can provide an effective remedy for these problems in unmatched case-control studies. We extend pooled exposure strategies to handle specimens collected in a matched case-control study. We show that if a logistic model applies to individuals, then a logistic model also applies to an analysis using pooled exposures. Consequently, the individual-level odds ratio can be estimated while conserving both cost and specimen. We discuss appropriate pooling strategies for a single exposure, with adjustment for multiple, possibly continuous, covariates (confounders) and assessment of effect modification by a categorical variable. We assess the performance of the approach via simulations and conclude that pooled strategies can markedly improve efficiency for matched as well as unmatched case-control studies.
From the Biostatistics Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC.
Submitted 14 December 2010; accepted 21 April 2011; posted 11 July 2011.
Supported by the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences (project ES040006-14).
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Correspondence: P. Saha Chaudhuri, Biostatistics Branch, National Institute of Environmental Health Sciences, P. O. Box 12233, Mail Drop A3-03, 111 T. W. Alexander Drive, Research Triangle Park, NC 27709. E-mail: firstname.lastname@example.org.