London School of Hygiene & Tropical Medicine

The analyses of randomised controlled trials with missing data typically assume that, after conditioning on the observed data, the probability of missing data does not depend on the patient's outcome. This assumption is usually implausible, for example becuase patients in relatively poor health may be more likely to drop-out. Methodological guidelines recommend that trials require sensitivity analysis, which is best informed by elicited expert opinion, to assess whether conclusions are robust to alternative assumptions about the missing data. A major barrier to implementing these methods in practice is the lack of relevant practical tools for eliciting expert opinion. We develop a new practical web-based tool for this purpose, and in this talk will demonstrate its use for RCTs with missing data using the IMPROVE trial.