Pragmatic approaches to mitigating missing data and research priorities to assess the effectiveness of interventions

Background Identifying interventions to minimise missing data was the third highest research priority in a Delphi survey of the Directors of UK Clinical Trial Units (CTUs). However, a Cochrane Methodology Review of nested randomised studies of missing data interventions shows a substantial evidence gap, with all but one of the eligible studies targeting questionnaire response rates. Research is needed to identify strategies that effectively address the broader causes of missing data, including minimising withdrawals, ensuring clinical staff capture vital outcome measurements and improving patient attendance at clinic visits.