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	Rapid Evidence Assessment	Ex-Ante Policy Appraisal	Realist Synthesis
Ämnesområde	Public Policy	Public Policy	Evidenssyntes
Familj	Process / pipeline	Process / pipeline	Process / pipeline
Ursprungsår	2013	2022	2005
Upphovsperson	UK Government Social Research Service with the EPPI-Centre	Public-finance appraisal tradition; codified by HM Treasury (Green Book)	Ray Pawson (2005)
Typ	Time-constrained systematic evidence synthesis	Structured ex-ante appraisal of policy options	Framework
Ursprungskälla	Government Social Research Service (2013). Rapid Evidence Assessment Toolkit. London: Civil Service / GSR, developed with the EPPI-Centre.	HM Treasury (2022). The Green Book: Central Government Guidance on Appraisal and Evaluation. London: HM Treasury.	Pawson, R., Greenhalgh, T., Harvey, G., & Walshe, K. (2005). Realist review—a new method of systematic review designed for complex policy and programme evaluation. Journal of Health Services Research & Policy, 10(S1), 21–35.
Alias	REA, Rapid Evidence Review, Rapid Evidence Synthesis	Policy Appraisal, Options Appraisal, Green Book Appraisal	Realist Review, CMO Configuration, Mechanism-Based Synthesis
Närliggande	2	4	1
Sammanfattning	A rapid evidence assessment (REA) is a way of getting on top of the available research evidence on a policy question as comprehensively as possible within the constraints of a short timetable. It uses the systematic and transparent methods of a full systematic review — explicit search strategies, inclusion criteria and quality appraisal — but deliberately limits the breadth of one or more stages to fit the time and resources available. Promoted in the UK by the Government Social Research Service and the EPPI-Centre, the REA was designed to give policymakers rigorous, accountable evidence syntheses on timescales that conventional systematic reviews cannot meet.	Ex-ante policy appraisal is the structured assessment of the costs, benefits, risks and trade-offs of alternative options for achieving a policy objective, carried out before a decision is taken. Codified in guidance such as the UK Treasury's Green Book, it provides a disciplined framework for deciding whether to intervene and, if so, how — by establishing the rationale and objectives, generating and narrowing a range of options, appraising each against a counterfactual, and recommending the option that offers best value for public money. Appraisal is the forward-looking complement to ex-post evaluation, which judges interventions after they have run.	Realist synthesis is a theory-driven, interpretive method for evidence synthesis developed by Ray Pawson (2005) that focuses on understanding HOW and WHY interventions work, rather than WHETHER they work. Grounded in realist philosophy, realist synthesis examines Context-Mechanism-Outcome (CMO) configurations: how specific contextual conditions activate mechanisms that produce outcomes. Unlike traditional systematic reviews, which typically answer 'Does intervention X reduce outcome Y?', realist synthesis asks 'Under what conditions, through what mechanisms, for which populations does X work?' This approach is particularly valuable for complex interventions (policies, programs, multi-component treatments) where effectiveness varies dramatically across contexts, and for understanding why interventions succeed in some settings but fail in others.