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2010 Dietary Guidelines Advisory Committee (DGAC) Nutrition Evidence Library Methodology


Government staff assisted the Committee members in the execution of the systematic review using the methodology outlined in Part C: Methodology of the 2010 Dietary Guidelines Advisory Committee Report. Below is a summary of the NEL evidence-based systematic review process and the division of duties between government staff and the Dietary Guidelines Advisory Committee.

For additional information on 2010 DGAC NEL methodology, see the following published article:

Spahn JM, Lyon JM, Altman JM, Blum-Kemelor DM, Essery EV, Fungwe TV, Macneil PC, McGrane MM, Obbagy JE, Wong YP. The systematic review methodology used to support the 2010 Dietary Guidelines Advisory Committee. J Am Diet Assoc. 2011 Apr;111(4):520-3. doi: 10.1016/j.jada.2011.01.005. PubMed PMID: 21443982.

NEL Process Steps

Brief Description

Government Staff Responsibilities

DGAC Responsibilities

Formulate the Question

Specify a question.  Define the Population, Intervention/cause, Comparitor and Outcome of interest (PICO chart development); define criteria for study selection

- Facilitate meetings

- Facilitate PICO chart development

- Conduct preliminary searches

-Recommend search strategies

- Populate sort list tool (e.g., search terms, inclusion & exclusion criteria)

- Define topic areas

- Draft questions to research

- Develop an analytical framework

- Define scope of question (PICO)

- Define inclusion and exclusion criteria for literature search and sort plan

Gather/classify evidence

Conduct and document a systematic search of the literature to find evidence related to the question; list systematic reviews and primary studies separately

- Facilitate meetings

- Conduct and document a systematic search of the literature

- List included systematic reviews and primary studies separately

- List excluded studies with rational

- Hand search manuscripts for additional citations

- Review/approve the sort list e.g., review inclusion/  exclusion criteria, databases and search terms used, included and excluded studies

- Describe critical components and table column headings to guide data extraction

Critically appraise each included study

Review studies for relevance to the question and critique for scientific validity.

Abstract key information to an evidence worksheet and determine the study quality rating (positive, negative, or neutral) based upon the Research Design and Implementation Checklist

- Facilitate meetings

- Build portal infrastructure

- Assign included articles to abstractors to draft evidence worksheets

- Perform quality review and finalize evidence worksheets

- Review the evidence summary paragraph for each study for accuracy and clarity

- Review overview tables for completeness and clarity

Summarize the evidence

Write a brief paragraph that summarizes the key data from each included study. Develop an overview table that displays key information from each study to answer the question.


- Facilitate meetings

- Draft a brief, easy-to-read evidence summary paragraph for each included study to report relevant, scientifically valid data

- Create an overview table based upon DGAC specifications

- Facilitate review of the evidence summary by all subcommittee members

- Update text in portal as instructed by DGAC members

- Create an evidence summary which synthesizes the available evidence. This may include:

   - A brief overall summary statement describing number and type of studies reviewed

   - Findings including agreement and disagreement among studies

   - Comparison factor statements e.g., differences in findings by gender, age, disease stage

   - Methodological statements

   - Impact of outcome

   - Definitions -  if needed can be added as glossary terms

- Bring to full DGAC for review/approval

Develop a conclusion statement and grade the strength of evidence supporting the conclusion

Develop a concise conclusion statement to answer the question based on a synthesis of all relevant studies and deliberation with subcommittee members.

Grade the strength of the evidence informing the conclusion statement using the 2010 DGAC Conclusion Grading Chart.

- Facilitate meetings

- Update text in portal as instructed by DGAC members

- Develop a conclusion statement, based upon a synthesis of the findings of all relevant studies

- Assign a grade to indicate the overall strength or weakness of evidence informing the conclusion statement

- Bring to DGAC for review/approval

Develop research recommendations

Develop research recommendations

-Facilitate meetings and input research recommendations in the computer

Develop research recommendations based on the review of literature


Last Updated: 01/17/2014