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How to Search in Biomedical Databases

Tutorials for Library Databases and Resources

Sample Search Step #7: Applying Filters & Adjusting your Initial Search

  • In the search example that was just run in the previous page, you'll note that there is a small set of four results. This is a good thing! Often, searches will either bring up too many results, or, even worse, none at all. 

  • To remove certain results from your final search, you will probably want to apply filters. This can even apply in the case of this search with only four results, and it especially applies in the case of searches that yield hundreds or thousands of results. 

  • To use PubMed filters, look on the left side of the results. As pictured below, there are options to filter your search by Article types, Publication dates, Language, Age, Gender, etc. To access the complete list of filters, click on the “Additional filters” link:

Screen capture highlighting filters for PubMed results, as well as the location of the "Additional Filters" link
  • Suppose that you only want results with human subjects. In the menu that opens after clicking on this "Additional filters" link, there should be an option labeled "Species," as highlighted below. Within the "Species" section, select the checkbox labeled "Humans" and then click on "Show."

Screen-capture of Additional Filters menu with Species selected
  • To finish applying the filter, click the check box for the filter labeled "Humans" on the search page, as pictured here. This should reduce your number of results:

Screen-capture showing where to click in order to turn the "humans" search filter on
  • Note: Use the PubMed built-in limits cautiously. Limits other than date or language will limit your search to indexed records only. In most cases it is best to develop another concept to use as a limiter. For example, if you would like to limit your results to "human studies," use the following search to exclude animal studies instead of using the "humans" limit from the search results page. Simply add this to the rest of your search strategy using the NOT Boolean operator

(animals[MeSH Terms] NOT humans[MeSH Terms])

Adjusting Your Search: Broadening Results by Removing a PICO Element

  • At this point, it might be worthwhile to adjust your search to make it either more specific or more broad. In the case of this search on Atorvastatin and memory loss, it makes sense to broaden the results because our search retrieved only four results. 
  • If we take out the search string for female, our search might retrieve results that are relevant to our clinical/research topic
  • Here's the search with only two concepts in the advanced search page, created using the same steps shown in the previous section:
Screencapture of search with only two concepts in the advanced search page query box
  • The complete search string, as pictured above:

("​Memory Disorders"[Mesh] OR "Memory Loss"[tiab] OR "Memory Disorder"[tiab] OR "Memory Disorders"[tiab] OR "Cognitive Retention Disorder"[tiab] OR "Cognitive Retention Disorders"[tiab] OR "Semantic Memory Disorder"[tiab] OR "Age Related Memory Disorder"[tiab] OR "Age Related Memory Disorders"[tiab] OR "Memory Deficit"[tiabOR "Memory Deficits"[tiab])


("​Atorvastatin"[Mesh] OR Atorvastatin[tiab] OR "(3R,5R)-7-(2-(4-Fluorophenyl)-5-isopropyl-3-phenyl-4-(phenylcarbamoyl)-1H-pyrrol-1-yl)-3,5-dihydroxyheptanoic acid"[tiab] OR "Atorvastatin Calcium"[tiab] OR "Atorvastatin, Calcium Salt"[tiab] OR Liptonorm[tiab] OR Lipitor[tiab] OR "Atorvastatin Calcium Hydrate"[tiab] OR "Atorvastatin Calcium Anhydrous"[tiab] OR "CI 981"[tiabOR "CI-981"[tiab] OR "CI981"[tiab] OR "Atorvastatin Calcium Trihydrate"[tiab])

  • Remove the string for females from our search, broadens our result list from four results to 27 results:
Screen-capture of PubMEd results page with 27 results