Framework for design and evaluation of complex interventions to improve health

Randomised controlled trials are widely accepted as the most reliable method of determining effectiveness, but most trials have evaluated the effects of a single intervention such as a drug. Recognition is increasing that other, non-pharmacological interventions should also be rigorously evaluated. 1-3 This paper examines the design and execution of research required to address the additional problems resulting from evaluation of complex interventions—that is, those “made up of various interconnecting parts. ”4 The issues dealt with are discussed in a longer Medical Research Council paper (www. mrc. ac. uk/complexₚackages. html). We focus on randomised trials but believe that this approach could be adapted to other designs when they are more appropriate. #### Summary points Complex interventions are those that include several components The evaluation of complex interventions is difficult because of problems of developing, identifying, documenting, and reproducing the intervention A phased approach to the development and evaluation of complex interventions is proposed to help researchers define clearly where they are in the research process Evaluation of complex interventions requires use of qualitative and quantitative evidence There are specific difficulties in defining, developing, documenting, and reproducing complex interventions that are subject to more variation than a drug. A typical example would be the design of a trial to evaluate the benefits of specialist stroke units. Such a trial would have to consider the expertise of various health professionals as well as investigations, drugs, treatment guidelines, and arrangements for discharge and follow up. Stroke units may also vary in terms of organisation, management, and skill mix. The active components of the stroke unit may be difficult to specify, making it difficult to replicate the intervention. The box gives other examples of complex interventions. #### Examples of complex interventions Service delivery and organisation: Stroke units Hospital at home Interventions directed at health professionals' behaviour: Strategies for implementing guidelines Computerised decision support Community interventions: Community …