Fig. 1

Typical limitations of knowledge transfer between worlds of policy and research: Research-based information about the effects of services flows from where it is collected (bottom right), typically from practice arenas where data are framed by research tools and analysed to maximise the internal validity of primary studies (bottom left), and then synthesised to emphasise average effects with an assessment of the degree of heterogeneity of studies and judgements about generalisability of findings. Subsequently summaries of syntheses are presented to panels, such as guideline groups, making policy decisions (top right). Information flow from policies to guide research base practice are interrupted during implementation efforts where evidence maximising external validity is required for systems issues, to complement evidence addressing practice issues (middle right)