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2010 DGAC Methodology: Class of Research

Classification of Reports1


Primary Reports



Secondary Reports



Randomized controlled trial (RCT)





Meta-analysis or Systematic review

Decision analysis

Cost-benefit analysis

Cost-effectiveness study



Cohort study


Nonrandomized trial with concurrent or historical controls

Case-control study

Study of sensitivity and specificity of a diagnostic test

Time series



Narrative review (Review article)

Consensus statement

Consensus report


Cross-sectional study

Trend Study

Case series

Case report

Before and after study



Medical opinion


Classifying studies and reports gives an initial picture of the type of studies and level of evidence available. It also helps organize the reports for critical appraisal.  Once the study design is identified and classified, this classification is then recorded on the article's worksheet template.

1Adapted by the American Dietetic Association from ©Joint Commission Resources: "A Practical Approach to Evidence Grading." Joint Commission Journal on Quality Improvement 2000:Volume 26(12):707