Initial searches are scoping exercises, giving an overview of the topic, placing your work in the context of already published studies and working out:
Initial searches also identify:
At this stage, skim the results to identify the above. Look at titles, abstracts, subject headings. Initial search strategies will be amended for relevancy and accuracy following feedback from this appraisal of results.
Break your topic down into constituent concepts. Depending on your topic, the PICO format may be used to identify the concepts:
Initial searches explore various keywords and subject headings and combinations of both.
Using key papers already known to you:
Search a relevant database and narrow your words to the titles of the articles. Look closely at the records:
Adapting the search strategy from a similar study:
You are ideally looking for a combination of keywords and subject headings to describe each aspect of the topic. Use OR to combine the words and subject headings which describe each aspect.
Finally combine the aspects together with AND.
To help clarify the logic of the search, it may help to consider it schematically. Identify and group the main keywords and subject headings.
This is a search derived from a systematic review entitled: “Systematic review of risk prediction models for falls after stroke.”
Use the thesaurus of subject headings within the various databases to identify relevant headings.
The subject headings are useful dictionary and thesauri to explore terms and definitions. In PubMed Medline, select the MeSH database to find additional relevant Medical Subject Headings to add to the keywords.
‘Systematic review of risk prediction models for falls after stroke’
In the published review, searches were conducted on seven databases (Medline, Embase, CINAHL, PsychINFO, Web of Science, Cochrane Library and SCOPUS. In accordance with best practice the published review presents all search strings as executed on all databases as supplemental data.
The table below gives a summary search strategy for this topic for PubMed Medline in Advanced mode using a combination of keywords and Medical Subject Headings to conduct a comprehensive search.
Stroke / brain trauma
|Stroke OR poststroke OR hemiplegia OR brain hemorrhage||“Cerebrovascular Disorders" OR "Cerebrovascular Trauma" OR "Stroke" OR "Brain Infarction"|
|Falls||Falls OR falling OR accident OR accidents OR slips OR trips OR tripped OR stumble OR||“Accidental Falls” OR “Accidents”|
|Risk||Risk OR prediction OR predictive OR score||"Risk" OR "Risk Assessment" OR "Risk Management"|
Searches #1 AND #2 AND #3 are combined to give a final result.
Appendix 2 of this guide gives the full versions of this full search for PubMed Medline and EMBASE databases.
 Walsh ME, Horgan NF, Walsh CD, et al Systematic review of risk prediction models for falls after stroke J Epidemiol Community Health 2016;70:513-519.
‘Topical non-steroidal anti-inflammatory drugs for analgesia in traumatic corneal abrasions’
OBJECTIVES: To identify and evaluate all randomised controlled trials (RCTs) comparing the use of topical NSAIDs with placebo or any alternative analgesic interventions in adults with traumatic corneal abrasions, to reduce pain, and its effects on healing time.
|Randomized controlled trial||
Randomized OR Randomised OR
|"Randomized controlled trial"|
|Eye, Eye Injuries||
Eye(s) OR Cornea(s) OR
|Anti Inflammatory Agents||
"anti inflammatory agents non steroidal" OR
Appendix 3 gives the published version of the full search as run on the OVID Medline database.
 Wakai A, Lawrenson JG, Lawrenson AL, et al Topical non-steroidal anti-inflammatory drugs for analgesia in traumatic corneal abrasions. Cochrane Database Syst Rev. 2017 May 18;5:CD009781. doi: 10.1002/14651858.CD009781.pub2.
‘Wound Cleansing for Pressure Ulcers’ 
Identify and group the main keywords and subject headings
Normal saline OR
Pressure ulcer* OR
Appendix 4 gives the published version of the full search as run on the CINAHL Ebsco database.
 Moore ZEH, Cowman S. Wound cleansing for pressure ulcers. Cochrane Database of Systematic Reviews 2005, Issue 4. Art. No.: CD004983. DOI: 10.1002/14651858.CD004983.pub2
There are various guides on how to develop search strategies on the library’s Libguides
https://libguides.rcsi.ie/findinginfo/litsearch Other methods of structuring searches such as the PICO method – Patient (or Participant or Population or Problem), Intervention, Comparison and Outcomes are outlined in the Cochrane Handbook (4.4.3).
Search strategies are created according to the specifications of the database, for example whether * or $ is the truncation symbol; whether subject heading searching is possible; range of filters/limits offered etc. See the on-screen help tutorials for each of the databases. Give yourself plenty of time to become familiar with the structure of the different databases.
 Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.1 (updated September 2020). Cochrane, 2020. Available at: : www.training.cochrane.org/handbook.
Looking out for other search terms / subject headings
See Scoping the topic, evaluate the first set of results and look out for:
Look at relevant records and identify the keywords and subject headings – make sure these are included in your search strategy.
Strategies vary between highly sensitive (high recall, but will retrieve irrelevant items) and highly specific (very precise, but may miss potentially relevant items)
The Cochrane Handbook (4.4.3) defines sensitivity versus precision as a balance between comprehensiveness and maintaining relevance.
 Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.1 (updated September 2020). Cochrane, 2020. Available at: www.training.cochrane.org/handbook.
Search Filters – sit on top on your subject searches
Carry out your subject searches first, evaluate and make sure you are happy with the relevancy of the results. Then apply an appropriate filter to focus or narrow the results further. Filters are often inbuilt into databases menus and search screens. In PubMed Medline for instance you can refine searches from a menu of “article Types” or “Clinical Query” study types. In the CINAHL database on EbscoHost for example you can select from a variety of “Clinical Queries or research designs such as “Randomized Controlled Trials.”
Cochrane for instance presents some highly sensitive search strategies for identifying randomized trials in PubMed, Embase and PsycInfo. Available at https://work.cochrane.org/pubmed/
Using Core Articles
Once you have identified the core articles, you can expand your results further by using:
Before running searching in other databases, be confident that you have refined your ideas and terms sufficiently to retrieve good results in the primary core database.
It is a complex task to “translate” a search from one database to another and requires a lot of time and effort. Essentially, you need to start again with each database. Find out about the database structure and use your exploration of keywords, subject headings and filters on one database to start exploring the next.
Each database provider (eg OVID, Ebsco) structures the databases differently.
Each database (Medline, CINAHL, PsycInfo, Embase) has a different set of subject headings.
Some databases (Web of Knowledge, SCOPUS, ERIC) don’t use subject headings, so you are relying on searching authors’ words – remember to think of different words to describe the topic.
The Cochrane Handbook has a comprehensive summary of sources and searching requirements and options in 4.S1 Technical Supplement to Chapter 4: Searching for and selecting studies .
Lefebvre C, Glanville J, Briscoe S, Littlewood A, Marshall C, Metzendorf M-I, Noel-Storr A, Rader T, Shokraneh F, Thomas J, Wieland LS. Technical Supplement to Chapter 4: Searching for and selecting studies. In: Higgins JPT, Thomas J, Chandler J, Cumpston MS, Li T, Page MJ, Welch VA (eds). Cochrane Handbook for Systematic Reviews of Interventions Version 6.1 (updated September 2020). Cochrane, 2020. Available from: www.training.cochrane.org/handbook.