A method for deciding early stopping of inconclusive case-control
studies in settings where data are stratified
Ulf Strömberg
University of Lund
Abstract
Statistical methodology for early stopping of clinical trials is
well developed. However, in epidemiological studies, methods for deciding
early stopping have rarely been considered. In contrast to clinical trials,
termination due to an early significant result is indeed seldom relevant,
because further expenditure is then likely to be worthwhile in order to
obtain a more precise effect estimate and to more precisely account for
confounders. On the other hand, if data obtained early indicate an
inconclusive final result and if continuation of the epidemiological study
is expensive, then it might be desirable to stop the study early. A method
is proposed for evaluating the possibility that an ongoing case-control
study will produce an inconclusive final result. The method is developed for
stratified case-control data. In principle, probable final results, given
the available data, are predicted by repeatedly simulating the remaining
data using plausible assumptions on the true exposure effect; these
assumptions should be in reasonable agreement with the available data.