Rapid reviews methods series: guidance on rapid scoping, mapping and evidence and gap map (‘Big Picture Reviews’)

Scoping, mapping and evidence and gap map reviews (‘Big Picture Reviews’ (BPRs)) are evidence synthesis methods that address broad research questions. They provide an overview of existing evidence, identify gaps in knowledge and priorities for research. Unlike systematic reviews (SRs) of effectiveness, they do not seek to synthesise findings but to provide a description of the evidence. There has been a growth in the production of rapid BPRs to meet commissioners’ and knowledge users’ (KUs) needs for timely outputs. No guidance currently exists for the use of rapid approaches in BPRs, and the purpose of this paper is to address this lack. Rapid reviews include simplifying or omitting a variety of methods; however, the approaches may have varying impacts on processes and findings in different types of reviews and should be done with reference to the standard approaches for that particular methodology. BPRs differ from SRs of effectiveness, in terms of their purpose, addressing a broad research question, rather than a specific question which fits a population, intervention, comparator and outcome (PICO) framework. Developing and refining the research question and search strategy may need more time than in a SR. Search yields are typically larger with a greater proportion of time spent on identifying evidence for inclusion when compared with SRs. They do not involve a synthesis of included studies, so the impact of missing data may have less influence on the rigour of the findings than in SRs of the effect of an intervention where a pooled estimate is reported. This paper addresses these differences, and the implications of rapid approaches to BPRs, with recommendations for practice that aim to increase efficiency while maintaining rigour.