Cochrane Work provides search strategies related to occupational health, providing filters for both professionals and researchers. HIRU (Mc Master's Health Information Research Unit) offers search strategies for researchers covering topics like prognostic, diagnostic, causation (etiology) and economics. Search manager lets you add unlimited search lines, view results per line and access the MeSH browser using the new MeSH button. AND OR NOT Title Abstract Keyword Record Title Abstract Author Keyword All Text Publication Type Source DOI Accession Number Trial Registry Number Cochrane Group Cochrane Topic.
Cochrane: Overview & Search Tips
We encourage students, researchers, and faculty members throughout Hopkins to use this overview of Cochrane for their research and instructional needs.
Contents
- Keywords (How to Find & Use Keywords)
- Controlled Vocabularies (MeSH, Trees & Subheadings)
- Combining Searches Using Boolean Operators (OR, AND, NOT)
Overview: When should I use this database?
The Cochrane Library is a collection of databases in medicine and other healthcare specialties provided by the Cochrane Collaboration and other organizations. At its core is the collection of Cochrane Reviews, a database of systematic reviews and meta-analyses which summarizes and interprets the results of medical research, which are often considered the “Gold Standard” for systematic reviews in terms of quality.
Before you start searching, keep in mind . . .
Save your search in a document, citation management software (Endnote, Refworks, etc.), and/or the database
- By saving your search, your strategy will be reproducible for another time and properly documented.
- Explore options for citation management here, and find tips on how to export results.
- To save searches and create alerts in Cochrane, create an account. Sign up for a Cochrane account by clicking here, or by clicking on the same link in the upper-right hand corner of the Cochrane homepage. Once logged in, go to the “Search Manager” tab (the tab directly to the right of the default “Search” tab). Towards the bottom of this page there are sections to enter “Strategy Name” and a link to save your strategy.
- To create an alert for a saved search strategy, expand the section on the “Search Manager” tab titled “Strategy Library.” In this section, select the checkbox for “Alerts”
Keywords
How to Find & Use
- Keyword terms can be single words or phrases.
- Use quotes around all phrases to ensure that the phrase is searched instead of each word individually. (e.g. “public health”)
- For more possible search terms, visit the MeSH database and look at the 'entry terms' listed for each MeSH record. These are synonyms, alternate forms, and other closely related terms generally used interchangeably with the preferred term.
- To find additional ideas and/or synonyms, consult controlled vocabularies in other subject databases. For example, Embase has a controlled vocabulary called Emtree. Emtree records contain synonym lists similar to the 'entry terms' in a MeSH record. The Emtree synonym list often contains European spellings/variations.
Controlled Vocabularies — How to Find & Use
Locate Controlled Vocabulary (MeSH)
- Cochrane relies on Medical Subject Headings (MeSH) from the National Library of Medicine, composed of a controlled vocabulary of biomedical terms used to describe the subject of each journal article. To access the hierarchical listing of terms, click on the “Medical Terms (MeSH)” tab or use the MeSH icon in the Search Manager.
- After typing in a term in the MeSH search box, matches to the MeSH thesaurus will be displayed along with structured trees that show the hierarchical relationships among related terms. A summary of search results from different Cochrane databases will also be displayed.
- Once you have selected your MeSH tree options, you can run it as a search by clicking the “Add to Search Manager” link. It will then be present in the “Search Manager” tab (second from the left).
Trees & Subheadings
- MeSH trees displayed in Cochrane allow you to visualize where your MeSH term sits in the hierarchy of terms and shows any branches off of your term. Selecting “Explode all trees,” allows you to search for your term and any terms that branch from it. Selecting “Single MeSH term (unexploded),” allows you to just search for your MeSH term without branches. If your MeSH term is part of multiple trees, you can select the specific trees you want to search by selecting “Explode selected trees.”
- A second search box gives you the option to 'Select subheadings / qualifiers.' Any MeSH can be made more specific by the addition of subheadings. These appear as a drop down menu similar to what’s described above for the “Enter MeSH term” box
Combining Searches Using Boolean Operators
- A comprehensive and systematic search of the Cochrane Library includes both controlled vocabulary and keyword terms (i.e. free text, natural language, and synonyms).
- Boolean operators are used to combine search terms. In Cochrane, you can use the operators AND, OR, and NOT.
- Boolean operators MUST be used as upper case (AND, OR, NOT).
- OR—use OR between similar keywords, like synonyms, acronyms, and variations in spelling within the same idea or concept
- AND—use AND to link ideas and concepts where you want to see both ideas or concepts in your search results
- NOT—used to exclude specific keywords from the search, however, you will want to use NOT with caution because you may end up missing something important.
- Go to the “Search Manager” page to combine searches. This is where your search history is located during your search session, and the plus and minus icons on the left side of the screen allow you to add/remove searches.
- To save searches and access your search history, sign up for a Cochrane account by clicking here.
Field Tags
You can use field tags to specify where the database looks for the search term. In Cochrane, first type the search term and then the field tag preceded by a colon. e.g. Cardiology :ti looks for cardiology in the title
:ti — Searches the Title field
:ab — Searches the Abstract field
:kw — Searches the Keyword field
![Library Library](/uploads/1/2/5/8/125821507/560010004.jpg)
:au — Searches the Author field
:so — Searches the Source field
:pt — Searches the Publication Type field
:tb — Searches the Tables field
Proximity Searching in Cochrane
- Cochrane allows for proximity searching through the use of two operators (NEAR or NEXT), along with a number to indicate the proximity of the words .
- Proximity search using NEAR: Use NEAR/ with a number to indicate proximity of terms either before or after each other. For example, “antidepressant NEAR/10 narcolepsy” looks for the word antidepressant within 10 words of narcolepsy. The default proximity value for the operator when no number is entered is 6.
- Proximity search using NEXT: Use NEXT to match terms that appear next to each other. E.g. cholera NEXT treat* would return “cholera treatment”
- Note that the apostrophe within a term is treated as a space. To search for adjacent words in a term such as Down's Syndrome, the best approach is to use NEAR instead of NEXT. The search parameter to use in this case would be: down* NEAR/2 syndrome
- Hyphenated terms: Hyphens are treated as a space with an associated NEXT operator. The term heart-related will match the same results as heart NEXT related. E.g. evidence-based NEXT medicine
Applying Filters
Cochrane will default your search results to Cochrane Reviews only. These results are often far fewer than the non-Cochrane Review results. To see all results, either click on the 'Search Limits' link beneath the search boxes on the main Search page, or go to the column to the right of the search results. This column should have options to select which type of result you wish to see (Other Reviews, Trials, Methods Studies, etc). Selecting some or all of these bubbles will show all results.
Truncation
- In Cochrane you can use a * at the root of a word to find multiple endings. For example:
arthroplast* will return arthroplasty, arthroplasties, arthroplastic, arthroplastics, etc.
mobili* will return mobility, mobilization, mobilisation, mobilize, etc.
- You can also use a ? as a wildcard to search for letter variants within a word (e.g. wom?n finds women and woman)
Additional examples of how truncation can be used (in combination with adjacency searching)
Type | Description | Example |
Terms with multiple spellings | Use the wildcard character with the NEXT operator to match all variations of a term. Note: Use NEAR between a word ending in 's' and another following word. | st* NEXT john* NEAR wort |
Diphthong characters | Terms with spelling variations that include diphthongs should be searched with a wildcard character to ensure that all forms of a term are matched. Some more common terms with diphthongs such as 'haemorrhage' are automatically matched to their variant spellings through stemming. | isch*mic stroke |
Accented characters | For all fields except Author, accented characters are not matched by their equivalent unaccented form. To match accented characters use the following options: 1) Use the wildcard characters (* or ?) for a broad match, 2) if the term is displayed on a page you are viewing, copy and paste it to the search box, 3) select the term from a list of accented characters. If entering an accented term in the search box, also include the unaccented version with an OR operator to match all cases. | Partial list of accent characters: ¤ Ì ‰ „ € ‡ ˆ ‹ Š Ê Œ ý Ž ÿ û ò º ü ù ¢ ÷ Ë Ÿ ¹ |
Wildcard truncation | Use an asterisk (*) to search for multiple characters before, within, or after a search string. A question mark can be used to search for a single character. | abdom* *eclampsia |
Accessing Full Text | ||
Cochrane provides full text access to all featured Cochrane Reviews directly within the database. For other research publications found within Cochrane (Other Reviews, Trials, Methods Studies, etc), simply click on the item in Cochrane and it should list options for accessing it externally. If Cochrane does not point you to a website providing full text, then try searching for the item from Welch’s homepage or from another medical database (PubMed, etc). |
More Information
- Search Help: http://www.thecochranelibrary.com/view/0/ccochnewsearch.html - includes links to “The Cochrane Library Search Tour” and “Understanding Search Error Messages”
- More detailed information about MeSH vocabulary is available at (https://www.nlm.nih.gov/mesh/) or (https://www.nlm.nih.gov/mesh/intro_retrieval.html)
See Also
Files & Handouts (for Instruction, Research, etc.)
Cochrane TipsheetAn instructional pdf containing search tips on how to use Cochrane for research. We encourage students, researchers, and faculty members throughout Hopkins to use it for their personal and instructional needs. |
Background
Systematic reviews collect, analyse and summarise research to answer defined research questions. The evidence from systematic reviews is considered as the most reliable evidence and is often used to inform healthcare-related decision making. Systematic reviews on prognosis, cause, risk factors and complications of a disease include a specific type of study design: observational studies. Searching for literature usually involves the use of MEDLINE and Embase databases and can result in a large number of articles to check for the review. Therefore, in order to focus their search, researchers often use a set of terms relating to study designs, known as methodological filters. However, when using these, researchers may miss relevant studies but find many irrelevant articles. Performance of filters are evaluated by sensitivity, which is the ability of the search filter to retrieve all the relevant studies that exist, and precision, which is the ability of the search filter to retrieve only relevant studies. Given the importance of including evidence from observational studies in systematic reviews, we aimed to assess studies evaluating methodological strategies for identifying observational studies in the two main databases of health literature, MEDLINE and Embase.
Study characteristics
We found two eligible studies reporting on 18 methodological filters, including six MEDLINE, six Embase and six combined MEDLINE/Embase filters. The firsts study focused on filters on observational studies of surgical interventions. The second study focused on filters for a specific subtype of observational studies: comparative non-randomised studies.
Key results
Six filters from the first study showed sensitivity of 99.5% to 100% and precision of 16.7% to 21.1%. One type of filter was evaluated by two additional systematic reviews (i.e. externally validated) and found that this retrieved 85.2% to 100% of the articles in the reference standard. Twelve filters from the second study had lower sensitivity (48% to 100%) and much lower precision (0.09% to 4.47%).
Quality of evidence
The included studies had several limitations. The first study used only one systematic review for search strategy development and focused on observational studies of surgical interventions, which might limit the generalizability of the findings to other literature searches. The reference standard in the second study, although encompassing four different systematic reviews, included a limited number of studies, which might affect the accuracy of the performance assessment. Both studies were published 10 years ago and labelling and indexing of observational studies has changed since then.
We found 18 methodological filters across two eligible studies. Search strategies from the first study had higher sensitivity and precision, underwent external validation and targeted observational studies. Search strategies from the second study had lower sensitivity and precision, focused on cNRSs, and were not validated externally. Given this limited and heterogeneous evidence, and its methodological limitations, further research and better indexation are needed.
Systematic reviews are essential for decision-making. Systematic reviews on observational studies help answer research questions on aetiology, risk, prognosis, and frequency of rare outcomes or complications. However, identifying observational studies as part of systematic reviews efficiently is challenging due to poor and inconsistent indexing in literature databases. Search strategies that include a methodological filter focusing on study design of observational studies might be useful for improving the precision of the search performance.
To assess the sensitivity and precision of a search strategy with a methodological filter to identify observational studies in MEDLINE and Embase.
Studies using a relative recall approach, i.e. comparing sensitivity or precision of a search strategy containing a methodological filter to identify observational studies in MEDLINE and Embase against a reference standard, or studies that compared two or more methodological filters.
Two review authors independently screened articles, extracted relevant information and assessed the quality of the search strategies using the InterTASC Information Specialists' Sub-Group (ISSG) Search Filter Appraisal Checklist.
We identified two eligible studies reporting 18 methodological filters. All methodological filters in these two studies were developed using terms from the reference standard records.
The first study evaluated six filters for retrieving observational studies of surgical interventions. The study reported on six filters: one Precision Terms Filter (comprising terms with higher precision while maximum sensitivity was maintained) and one Specificity Terms Filter (comprising terms with higher specificity while maximum sensitivity was maintained), both of which were adapted for MEDLINE, for Embase, and for combined MEDLINE/Embase searches. The study reported one reference standard consisting of 217 articles from one systematic review of which 83.9% of the included studies were case series
The second study reported on 12 filters for retrieving comparative non-randomised studies (cNRSs) including cohort, case-control, and cross-sectional studies. This study reported on 12 filters using four different approaches: Fixed method A (comprising of a fixed set of controlled vocabulary (CV) words), Fixed method B (comprising a fixed set of CV words and text words (TW)), Progressive method (CV) (a random choice of study design-related CV terms), and Progressive method (CV or TW) (a random choice of study design-related CV terms, and title and abstracts-based TWs). The study reported four reference standards consisting of 89 cNRSs from four systematic reviews.
The six methodological filters developed from the first study reported sensitivity of 99.5% to 100% and precision of 16.7% to 21.1%. The Specificity Terms Filter for combined MEDLINE/Embase was preferred because it had higher precision and equal sensitivity to the Precision Terms Filter. The 12 filters from the second study reported lower sensitivity (48% to 100%) and much lower precision (0.09% to 4.47%). The Progressive method (CV or TW) had the highest sensitivity.
There were methodological limitations in both included studies. The first study used one surgical intervention-focused systematic review thus limiting the generalizability of findings. The second study used four systematic reviews but with less than 100 studies. The external validation was performed only on Specificity Terms Filter from the first study Both studies were published 10 years ago and labelling and indexing of observational studies has changed since then.