[Development, appraisal and synthesis of complex interventions - a methodological challenge].

BACKGROUND: Many medical interventions are of a complex nature. They comprise interdependent components differently interacting within various complex settings, e.g., stroke units. Appraising the efficacy, benefit and harm of complex interventions is far more difficult than appraising single interventions like specific drug treatments. Detailed methodological procedures for the development, appraisal and synthesis of complex interventions are increasingly discussed internationally.
METHODS: Systematic inventory of methodological guidance for the development and evaluation of complex interventions through searching scientific literature databases and web resources of international institutes. Review of the current state of discussion and suggestions for the development, appraisal and synthesis of complex interventions.
RESULTS: Five methodological guidance papers have been identified. In particular, the UK Medical Research Council's guidance offers a structured introduction to the development and evaluation of complex interventions in health care and medicine. Synthesis of complex interventions using customary methods of systematic reviews is not satisfying. Other approaches to synthesis like realist evaluation as well as statistical procedures exploring the active components of complex interventions have been discussed. However, post hoc analytical procedures could never adequately replace careful prospective development and exploration of complex interventions and interdependencies with contextual factors.
CONCLUSION: Complex interventions require multi-stage development, use of different methods, reporting on all developing phases and new approaches for synthesis. Presentation of the complete evidence on a specific complex intervention might be more useful than synthesis of a variety of different complex interventions by customarily applied methods of (meta-analytical) systematic review.