Background: Primary care physicians hold a strategic position in delivering preventive services. However discrepancies exist between evidence based guidelines and practice.
Objectives: To assess the effects of interventions to improve the delivery of preventive services in primary care.
Search strategy: We searched the Cochrane Effective Practice and Organisation of Care Group specialised register (November 1995; August 1999), MEDLINE (1980 to 1995) and hand searched relevant journals.
Selection criteria: Randomised trials, controlled before and after studies, and interrupted time series analyses of interventions to improve preventive services by primary care professionals responsible for patient care.
Data collection and analysis: Two researchers independently extracted data and assessed study quality.
Main results: Fifty-five studies were included, involving more than 2000 health professionals and 99,000 people, with 83 comparisons between intervention and control groups. Post intervention differences between intervention and control groups varied widely within and across categories of interventions. Most interventions were found to be effective in some studies, but not in others. Five comparisons of group education versus no intervention showed absolute change of preventive services varying between -4% and +31%. Nine comparisons of physician reminders versus no intervention showed absolute change of preventive services varying between 5% and 24%. Fourteen comparisons of multifaceted interventions versus no intervention showed absolute change of preventive services varying between -3% and +64%. Six comparisons of multifaceted interventions versus group education reported absolute changes varying between -31% and +28%. All these comparisons used randomised groups. Ten comparisons of multifaceted interventions versus no intervention used non-randomised groups and showed absolute change of preventive services varying between -5% and +21%. The remaining planned comparisons within categories of interventions contained less than five comparisons.
Reviewer's conclusions: There is currently no solid basis for assuming that a particular intervention or package of interventions will work. Effective interventions to increase preventive activities in primary care exist, but there is considerable variation in the level of change achieved, with effect sizes usually small or moderate. Tailoring interventions to address specific barriers to change in a particular setting is probably important. Multifaceted interventions may be more effective than single interventions, because more barriers to change can be addressed. Future research should analyse barriers to change and interventions to implement preventive services in more detail, to clarify how interventions relate to specific barriers. Since more complex interventions are likely to be more effective but also more costly, economic evaluations should also be included.