Nutritional Research Series:
Advancing the Role of Evidence-based Reviews in Nutrition Research and Applications
Volume 1: Application of Systematic Review Methodology to the Field of Nutrition
Agency for Healthcare Research and Quality
Available online as PDF file [36p.] at: http://www.ahrq.gov/downloads/pub/evidence/pdf/nutrition/nutrtp1.pdf
“…..Systematic reviews represent a rigorous and transparent approach of synthesizing scientific evidence that minimizes bias. They evolved within the medical community to support development of clinical and public health practice guidelines, set research agendas and formulate scientific consensus statements. The use of systematic reviews for nutrition related topics is more recent. Systematic reviews provide independently-conducted comprehensive and objective assessments of available information addressing precise questions. This approach to summarizing available data is a useful tool for identifying the state of science including knowledge gaps and associated research needs, supporting development of science-based recommendations and guidelines, and serving as the foundation for updates as new data emerge.
Our objective is to describe the steps for performing systematic reviews and highlight areas unique to the discipline of nutrition important to consider in data assessment. Steps involved in generating systematic reviews include identifying staffing and planning for outside expert input, forming a research team, developing an analytic framework, developing and refining research questions, defining eligibility criteria, identifying search terms, screening abstracts according to eligibility criteria, retrieving articles for evaluation, constructing evidence and summary tables, assessing methodological quality and applicability, and synthesizing results including performing meta-analysis, if appropriate.
Unique and at times challenging, nutrition related considerations include baseline nutrient exposure, nutrient status, bioequivalence of bioactive compounds, bioavailability, multiple and interrelated biological functions, undefined nature of some interventions, and uncertainties in intake assessment. Systematic reviews are a valuable and independent component to decision making processes by groups responsible for developing science-based recommendations and policies….”
Chapter 1. Introduction
Examples of recent systematic reviews of nutrition related topics
Chapter 2. Systematic Review Methodology
Form multidisciplinary research team
Plan for outside inputs
Develop analytic framework
Develop and refine research questions
Define eligibility criteria
Identify search terms
Perform literature search
Evaluate search results
Construct evidence and summary tables, and extract data
Assess methodological quality and applicability of studies
Perform meta-analysis, as appropriate
Chapter 3. Discussion
Unique Considerations When Conducting Nutrition-Related Systematic Strengths and Limitations of Systematic Review Approach for Nutrition Reviews
Bioequivalence of Different Chemical Forms of Nutrients
Bioavailability of Nutrients
Multiple and Interrelated Biological Functions of a Nutrient
Undefined Nature of Nutrient Intervention
Uncertainties in Assessing Dose Response Relationships
Chapter 4. Conclusion
“…..Nutrient reference values have significant public health and policy implications. Given the importance of defining reliable nutrient reference values, there is a need for an explicit, objective, and transparent process to set these values. The Tufts Medical Center Evidence-based Practice Center assembled a group of nutrition experts from academic institutions and federal government agencies, led participants in discussions, conducted exercises in formulating questions and evidence review criteria that would be amenable to systematic reviews of the scientific literature, performed a literature search on the questions to identify potentially relevant publications, and identified challenges and limitations of applying this method to support the development of nutrient reference values, using vitamin A as an example.
The workgroup concluded that the systematic review approach could be productively used to inform the development of reference values. Challenges identified in this exercise include prioritizing and defining research questions when the volume of literature is large, relying on intermediate (surrogate) outcomes when few or no studies directly linked nutrient intake with clinical outcomes are available, and determining reliable nutrient biomarkers. Ultimately, an objective, unbiased systematic review of a defined question could be useful; not only in helping to set nutrient reference values, but also for increasing the transparency of the decision making process.
Background: The quality of nutrition-related systematic reviews (SR) is an unstudied but important factor affecting their usefulness.
Objective: To evaluate reporting quality of published SRs and identify areas for improvement.
Design: Descriptive and exploratory analyses of reporting quality (7 nutrition items and 28 SR reporting items) of all English-language SRs published through July 2007 linking micronutrients and health outcomes in humans. Factors that may to be associated with the reporting quality were also evaluated.
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