Research Guides: Systematic Review: Developing a Search Strategy

Developing a Search Strategy

A path covered with well aligned green, yellow and red apples flowing out of a basket

Image: Pinterest

Techniques for search term harvesting

Begin brainstorming search terms by using the following techniques:

Explore gold standard articles supplied by the principal investigator or found through preliminary searches.
Look at search strategies from published systematic reviews.
Scan records, articles, and searches for usable controlled vocabulary and natural language. Use database tools (e.g. thesauri, index, subject headings) to find controlled vocabulary terms; Oxford English Dictionary to locate word variants or synonyms, Text Mining tools to find Medical Subject Headings (MeSH) terms or "implicit" keywords.
Try Elicit to generate a few options for your initial research topic and narrow it down to a specific population, geographical location, disease, etc. You may explore similar tools, LitSense or CitationChaser to identify additional search terms.

Look for relevant and/or frequently occurring terms. List all terms in an Excel harvesting form.

Example:

cancer[Title/Abstract]
neoplasm[MeSH]
malignant[Text word]
tumor[All fields]

Learn how to build the search with the PubMed Tutorial. Test out the new feature: proximity searching.

Try 2Dsearch as an alternative to conventional "advanced search."

Instead of entering Boolean strings into one-dimensional search boxes, queries are formulated by manipulating objects on a two-dimensional canvas. This eliminates syntax errors, makes the query semantics more transparent, and offers new ways to collaborate, share, and optimize search strategies and best practices.

Translating search strategies across databases

ChatGPT
Ask ChatGPT using this prompt, "Covert this search into terms appropriate for the [name] database." Further reading:
Wang, S., Scells, H., Koopman, B., & Zuccon, G. (2023). Can ChatGPT write a good boolean query for systematic review literature search?. arXiv preprint arXiv:2302.03495.
LitSonar
Use the Help section for further guidance on how to use this tool (https://litsonar.com/help). Capable of searching eight different databases simultaneously
Polyglot
Use the Polyglot tool to translate search strings from PubMed across multiple databases. Access the tool's tutorial for more information (https://sr-accelerator.com/#/help/polyglot).
MEDLINE Transpose
Use this tool to translate your MEDLINE (PubMed) search to MEDLINE (Ovid) format or vice versa.
Database Syntax Guide
Guide to translating syntax for multiple databases. From Cochrane.

_____________________________________________________________

Take control of your search and turn off Pubmed's Automatic Term Mapping (ATM)! It will not include all variant terminology and automatically explodes MeSH terms. Not using ATM allows for clearer documentation of the search method.

For more information on Automatic Term Mapping, watch the video below.

Text Mining Tools

These tools can help you with building your search strategy.

PubMed Pub ReMiner - Text mining for PubMed to look at commonalities between MeSH terms and keywords
Go PubMed - Text mining tool for PubMed or MeSH terms. This article explains the features of this text mining tool.
PubVenn - This tool enables you to explore PubMed using venn diagrams. Also, try Search Workbench.
Yale MeSH Analyzer - Watch this tutorial (7 min.). This tool allows users to enter up to 20 PubMed ID numbers, which it uses to aggregate the metadata from the associated articles into a spreadsheet. For systematic reviews, it is useful in search strategy development to quickly aggregate the Medical Subject Heading (MeSH) terms associated with relevant articles. While it only works for PubMed, it can be useful for developing searches in medical-adjacent fields, such as psychology, nutrition, and animal health.
NCBI MeSH on Demand identifies MeSH® terms in your submitted text (abstract or manuscript). MeSH on Demand also lists PubMed similar articles relevant to your submitted text.
HelioBLAST - This tool finds text records that are similar to the submitted query. Your query is searched against the citations (abstract and titles) in Medline/PubMed and the top matching articles are returned in the results.
Coremine - It is ideal for those seeking an overview of a complex subject while allowing the possibility to "drill down" to specific details. Instructions
Carrot2 - This tool can automatically organize search results into topics. It can query PubMed and allows boolean searching.
SWIFT-Review - Desktop text mining tool specific to systematic reviews. To obtain your free license for SWIFT Review, simply browse to the Sciome Software web page to login and/or create your SWIFT-Review account.
Voyant - General text mining (this is the download). For the web version go to http://voyant-tools.org
TerMine - General text mining
JSTOR Text Analyzer - Recommends journal articles in JSTOR relevant to text.
CREBP-SRA Word Frequency Analyser (WFA) - This tool helps determine which words you should use to construct and refine a search strategy
Medline Ranker requires a set of known relevant records with PubMed identifiers and a test set of records (e.g. search results from a highly sensitive search). Medline Ranker sorts the records in the test set and presents those that were most similar to the relevant records first. Medline Ranker also provides a list of discriminating terms which discriminate relevant records from non-relevant records.

_________________________________________________________________________

For more information on text mining tools - review and comparison, read the following article:

Paynter, R., Bañez, L. L., Berliner, E., Erinoff, E., Lege-Matsuura, J., Potter, S., & Uhl, S. (2016). EPC methods: an exploration of the use of text-mining software in systematic reviews.

Flying books through a filter and a small pile of books on the other side of the filter

Image modified from www.buzzfeed.com, image #24

Search Filters / Hedges

Search hedges are vetted strategies created by expert searchers to find specific literature.

Keep in mind!

Date of creation of filter
Pace of change in terminology (controlled and free text)

If you edit a filter, note this in the manuscript.

Example:

“We used a prognosis filter based on that developed by Smith (2015).”

You might limit to a particular publication type in Pubmed. See a full list of Pubmed publication types.

ASTED3S - Directory of search strategy concepts This collaborative platform from a special committee of librarians from ASTED3S aims to share various documentary tools developed by libraries in health and social services (3S). It was set up to encourage the sharing of expertise and resources as well as to pool the efforts made to support users.
CADTH Database Search Filters A list of commonly used filters from the Canadian Agency for Drugs and Technologies in Health (CADTH). Note that these filters have not been validated against a gold standard set of articles, and should probably not be used for a systematic review, but may be useful for other types of reviews.
Cochrane Handbook
Part 2, Section 6.4.11 provides search filters to limit to randomized controlled trials in Medline/PubMed, Medline/Ovid, and Embase
Collaborative Directory of Documentary Resources of Quebec Health and Social Services Libraries This directory brings together strategic concepts related to the field of health and social services developed by information professionals or research experts. Their production context being variable (exploratory reviews, systematic reviews, watches, etc.), they should be considered as a starting point. Moreover, since database thesauri evolve rapidly, validation of descriptors is required.
InterTASC Information Specialists' Sub-Group Search Filter Resource Filters for CINAHL, Embase, Medline, PsycINFO, and PubMED. Some of the areas covered are Adverse events, Diagnostic studies, Economic evaluations, Epidemiological studies, Etiology, Non-randomized studies, Observational studies, Outcome studies, Prognosis, Qualitative research, Quality of life, RCTs and other trials, Systematic reviews, Therapy studies, and others.
Literature Search Hedges & Filters - Univ. of Texas by Laurissa Gann
McMaster - Filters by the Hedges team
Ovid Expert Searches* This page is intended to provide some hints, advice and suggestions about how search strategies might be built, not to act in place of strategies built with expert subject knowledge or the assistance of a Medical Librarian.
PubMed Clinical Queries Table of Filters The clinical queries section of PubMed is based on validated search filters which are explained in this table.
PubMed Search Strategies Blog "This blog has been created to share PubMed search strategies. Search strategies posted here are not perfect. They are posted in the hope that others will benefit from the work already put into their creation and/or will offer suggestions for improvements."
PubMed Systematic Review Filter Search Strategy
Search Filters by study design Harvard Library
Search Filters from Univ. of Texas School of Public Health
SIGN (Scottish Intercollegiate guidelines network) Filters for CINAHL, Medline, and Embase in the areas of: Systematic Reviews, Randomised Controlled Trials, Observational Studies, Diagnostic Studies, Economic Studies, and Patient issues
University of Alberta Health Sciences Search Filters UofA has developed a series of filters not only for identifying particular study types, but also to retrieve literature on particular geographic locations (Canada) and populations (Indigenous Peoples, homeless people, pediatrics, geriatrics). There are also filters for a diversity of frequently searched topics (euthanasia, emergency department, social media, etc.).
Systematic Reviews: Search Filters / Hedges Advice: Don't limit by study methodology unless you have to! This is because in most cases, such limits result in missing relevant studies due to 1) large variety of terms used to describe study types 2) many authors never mention methodologies in title/abstract 3) inconsistent indexing in particularly for non-randomized designs. If retrieved results are unmanageable and you need a methodology filter, use validated filters that have been tested against gold-standard sets.

Hedges by Topic (in alphabetical order)

Health Disparities
- Prady, S. L., Uphoff, E. P., Power, M., & Golder, S. (2018). Development and validation of a search filter to identify equity-focused studies: Reducing the number needed to screen. BMC Medical Research Methodology, 18(1), 106. https://doi.org/10.1186/s12874-018-0567-x
Health Risk Assessment by Vicky Tessier at the INSPQ
Interventions/programs by Vana Ké:
- Effectiveness of Interventions
- Prevention
Animal studies
- van der Mierden, S., Hooijmans, C. R., Tillema, A. H., Rehn, S., Bleich, A., & Leenaars, C. H. (2022). Laboratory animals search filter for different literature databases: PubMed, Embase, Web of Science and PsycINFO. Laboratory animals, 56(3), 279–286. https://doi.org/10.1177/00236772211045485

A hand checking a box next to Excellent. Other bullets under the performance heading are good and poor.

Image by Steven Hunt

Evaluating Your Search Strategy

To find any nesting errors, use BalanceBraces.com and check the "Parentheses" option.

Check your search strategy for any errors using the checklist below.

Updated Press Checklist (2015)
See page 41-42
IOM Standards for Systematic Reviews
PRESS Peer Review of Electronic Search Strategies: 2015 Guideline Statement It is believed that quality is enhanced when there is peer review of the electronic search strategies developed for systematic review (SR) and health technology assessment (HTA) reports. The PRESS Guideline provides a set of recommendations concerning the information that should be used by librarians and other information specialists when they are asked to evaluate these electronic search strategies. This guideline updates and expands upon the 2008 CADTH report PRESS: Peer Review of Electronic Search Strategies, as well as An Evidence Based Checklist for the Peer Review of Electronic Search Strategies (PRESS EBC), published in the Evidence Based Library and Information Practice journal in 2010.

PRESS Checklist

Source:

McGowan J, Sampson M, Salzwedel DM, Cogo E, Foerster V, Lefebvre C. PRESS Peer Review of Electronic Search Strategies: 2015 guideline statement. Journal of Clinical Epidemiology, 75, 40-46.

Graphics with three overlapping paper sheets

Image by http://www.duluthtownship.org

Documenting Your Search Strategy

Keep track of all your search terms and search strategies that you have used for each database.

You will need this information as supplemental material to accompany your manuscript.

Read more about how to present your search strategy: Line by Line vs Block by Block vs Single-Line.

Register your search strategy at https://www.searchRxiv.org

Systematic Literature Review Worksheet

Use the Database Search Log to record your search terms, search strategy and databases searched.

Guidance on Reporting Systematic Reviews

Cochrane strongly encourages that review authors include a study flow diagram as recommended by the PRISMA statement.

Other checklists include:

Equator Network list of guidelines - Browse for reporting guidelines by study type, clinical area, and section of report. Some examples include:
- ARRIVE and DSPC for animal studies
- MOOSE - meta-analysis of observational studies in epidemiology
- STARLITE - general health policy and clinical practice
- TIDier-PHP - population health and policy interventions

Examples of documented search methodologies:

Full search strategies for all database searches provided in the Appendices:

Bath, P. & Krishnan, K. (2014). Interventions for deliberately altering blood pressure in acute stroke. Cochrane Database of Systematic Reviews, 10.

A summary of sources searched and keywords used in the Sources section:

McIntyre, S, Taitz, D, Keogh, J, Goldsmith, S, Badawi, N & Blair, E. (2013). A systematic review of risk factors for cerebral palsy in children born at term in developed countries. Developmental Medicine & Child Neurology, 55(6), 499-508.

Callout with the word Blog inside over the heads of people

Image by Eternal allegiance

Blogs & Discussion lists

Learn from other experienced searchers and get professional advice from the library community.

ACRL Systematic Reviews & Related Methods Interest Group
acr-srrmig@lists.ala.org
Cindy Schmidt's Blog: PubMed Search Strategies
This blog has been created to share PubMed search strategies. Search strategies posted here are not perfect. They are posted in the hope that others will benefit from the work already put into their creation and/or will offer suggestions for improvements.
MedTerm Search Assist from the University of Pittsburgh
By librarians for librarians - A database to share biomedical terminology and strategies for comprehensive searches.
MLA expert searching discussion list
expertsearching@pss.mlanet.org - This discussion list often discusses subject strategies and sometimes search filters.
PRESS Forum
This closed wiki-based forum is a place for librarians to request reviews of systematic review search strategies, and to review the searches of others.

Systematic Review

Workshop materials

Book

Errors in search strategies