METAPOW: Stata module for simulation based sample size calculations for designing new clinical trials and diagnostic test accuracy studies to update an existing meta-analysis

The metapow package contains a suite of programs which enable the user to estimate the probability the conclusions of a meta-analysis will change with the inclusion of a new study(ies). Using the -metasim- program, a simulation approach to estimating the effects in future studies is taken. The method assumes that the effect sizes of future studies are consistent with those observed previously, as represented by the current meta-analysis. Both the contexts of two-arm randomised controlled trials and studies of diagnostic test accuracy are considered for a variety of outcome measures. Calculations are possible under both fixed and random effect assumptions and several approaches to inference including statistical significance and limits of clinical significance are possible. Calculations for specific sample sizes can be conducted (using -metapow-), and plots, akin to traditional power curves, indicating the probability a new study(ies) will change inferences for a range of sample sizes can be produced (using -metapowplot-). We hope the package will be useful to i) trialists who want to assess the impact potential new trials will have on the overall evidence base; and ii) meta-analysts who want to assess the robustness of the current meta-analysis to the inclusion of future data.