title: Inverse sampling of controls in a matched case control study.
abstract: A method of inverse sampling of controls in a matched case-control study is described in which, for each case, controls are sampled until a discordant set is achieved. For a binary exposure, inverse sampling is used to determine the number of controls for each case. When most individuals in a population have the same exposure, standard case-control sampling may result in many case-control sets being concordant with respect to exposure and thus uninformative in the conditional logistic analysis. The method using inverse control sampling is proposed as a solution to this problem in situations when it is practically feasible. In many circumstances, inverse control sampling is found to offer improved statistical efficiency relative to a comparable study with a fixed number of controls per case.
authors.affiliation: Cancer Research UK Epidemiology Unit, University of Oxford, Oxford OX3 7LF, UK. ruth.keogh@ceu.ox.ac.uk
authors.forename: R H
authors.initials: RH
authors.lastname: Keogh
mesh_terms: D016022:Case-Control Studies; D003627:Data Interpretation, Statistical; D006801:Humans; D016015:Logistic Models