B1190
Title: Design2phase library to estimate power and efficiency of a two-phase design with survival outcome
Authors: Francesca Graziano - University of Milano-Bicocca (Italy) [presenting]
Paola Rebora - Universita Milano Bicocca (Italy)
Abstract: The availability of large epidemiological cohorts and stored biological specimens allows re-use these data to answer new research questions. Two-phase sampling is a general approach for sub-sampling that significantly reduce the time and cost of the study. The lack of easily available tools in the selection of the most efficient and powerful sub-cohort is, however, one of the main limitations. The design2phase library, implemented in R software, is a tool that provides a simulation-based investigation of sub-sampling performances with the aim of estimating the association between a new marker and a time-to-event outcome in a two-phase study. The library was created to estimate the power and efficiency of a wide variety of sampling designs (simple random sampling, case-control, probability proportional to size, nested case-control, and countermarching) applying a two-phase Cox model weighted by the inverse of the empirical inclusion probability. This user-friendly tool also gives the possibility to perform stratified sampling and to visualize power curves, and therefore it could be used by the researchers during the planning phase. The statistical background is briefly reviewed and the functions are illustrated on real data on childhood acute lymphoblastic leukemia, to evaluate the role of different genetic polymorphisms on treatment failure due to relapse.
