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Evidence-Based Medicine: Review and Practice: Filtering by study design

Created by Health Science Librarians

Filter Search Results by Appropriate Study Design

Look for articles in the search result that have the highest level of evidence for your type of question.
  • For prevention or treatment questions, start The optimal types of evidence are: meta-analysis of RCTs for a therapy/prevention question, cohort studies for an etiology/harm question, a comparison to a reference standard with reported sensitivity/specificity for diagnostic questions, and cohort studies for prognostic questions
    by searching for evidence at the top of the list,
    systematic reviews of randomized trials.

If no evidence is found at the top levels, move down the list looking for systematic reviews and then single studies of first cohort studies and then case-series or case-control studies.

  • For some types of clinical questions, a randomized controlled trial is not an option.  For etiology / harm or prognosis questions, start with cohort studies.
PubMed has Year and Article Type filters on the left side of the results page








Consider the publication date in the selection process.

If the systematic review you find was published a number of years ago
and found inconclusive evidence, then look for newer randomized trials
as your next step.

Small result sets can be filtered “by eye”.​ For larger result sets, use search filters.

In PubMed, you can access filters for Article Type, Publication Date, Age, Language,
and other filters on the left side of the search results page.  If you do not see the
filters or options you want, you can click the Additional Filters button at the bottom
of the filters menu to add more items to the menu.