Nutrition Evidence Library Systematic Review Methodology
NEL systematic reviews (SRs) are designed to address food and nutrition-related topics that are important to Federal government policy and program decision-making. The processes NEL uses to identify topics and develop SR questions are designed to ensure the utility of NEL SRs, by leveraging a broad range of expert input (i.e., both scientists and Federal program and policy-makers) to identify, refine and prioritize the most relevant and important topics. This input is then used to develop clearly focused SR questions which are appropriate in scope, reflect the state of the science, target important policy relevant to public health issue(s), and do not duplicate high-quality existing reviews. Once topics and questions have been generated, a group of subject matter experts is convened to conduct SRs. Their first step is to develop analytical frameworks to refine the SR questions and illustrate the overall scope of the SR project.
Question and Analytic Framework Development
A Closer Look: Systematic Review Questions
The core elements of a SR question are identified: Population, Intervention or Exposure, Comparator and Outcomes (PICO), and preliminary SR question(s). The SR question(s) should reflect important decisional dilemmas in public health nutrition guidance and reflect what decision makers need to make evidence-based policy and program decisions. SR questions must be specific enough to be researchable using NEL methodology, but broad enough to not overly limit the scope of the literature search. The PICO represents key aspects of the topic that need to be considered in developing a SR framework.
- Population: Population(s) of interest, and any relevant subpopulations
- Intervention: Intervention(s) and/or exposure(s) [independent variable(s)] of interest
- Comparator: Main comparison(s) of interest [e.g., main alternative(s) to compare with the intervention(s) or exposure(s)]
- Outcomes: Public health outcomes (e.g., health or diet-related outcomes) of interest (dependent variables)
An analytical framework is a type of evidence model that defines and links populations, interventions or exposures and the comparators, intermediate outcomes, and clinical health outcomes, as well as identifies key confounders to consider. It serves as a visual representation of the overall scope of the project, provides definitions for key SR terms, helps to ensure that all contributing elements in the causal chain will be examined and evaluated, and aids in determining inclusion and exclusion criteria and the literature search strategy. The following is an example of an analytical framework:
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Last Updated: 01/24/2014