Identifying synonyms
Once you have used PICO to identify the key concepts you are searching for, the next step is to identify synonyms and other related terms.
Different authors may use different words to refer to the same concept so it is important to search for a variety of terms in order to reduce the chance of missing important research. For example, one piece of research might refer to bitches but another might refer to dogs.
Thinking about the example in EBVM Toolkit 1 an extended PICO could include the following keywords:
| PICO componet | Question concept | Synonyms and other relevant key words |
|---|---|---|
| Patient or population | adult bitches | dog, dogs, bitch, bitches, canine |
| Intervention | neutering | spaying, neutering, ovariohysterectomy, ovariectomy, gonadectomy |
| Comparison/control | no intervention | not applicable |
| Outcome | mammary tumours | mammary, breast, tumour, cancer, neoplasia, neoplasm, mass, lump, carcinoma |
Truncation
You then need to select the key search terms, remembering to think of alternative spellings and the different endings to words e.g. plurals that may have been used. See below where an asterisk indicates truncation.
See below for more information on using truncation symbols [to add].
| PICO componet | Synonyms and other relevant key words |
|---|---|
| Patient or population | dog, dogs, bitch*, canine |
| Intervention | spay*, spey*, neuter*, ovariohysterectom*, ovariectom*, gonadect* |
| Comparison/control | not applicable |
| Outcome | mammar*, breast*, tumour*, tumor* cancer, cancers, neoplas*, mass, masses, lump, lumps, carcinom* |
Combining keywords
Then we need to think about how we would combine the keywords using AND, OR and NOT.
See below for more information on combining keywords [add this].
| PICO componet | Synonyms and other relevant key words |
|---|---|
| Patient or population | (dog OR dogs OR bitch* OR canine) |
| Intervention | (spay* OR spey* OR neuter* OR ovariohysterectom* OR ovariectom* OR gonadect*) |
| Comparison/control | not applicable |
| Outcome | (mammar* OR breast*) AND (tumour* OR tumor* OR cancer OR cancers OR neoplas* OR mass OR masses OR lump OR lumps OR carcinom*) |
You need to be careful how you combine the keywords as different combinations will produce different results.
Some databases have an advanced search option which allows you to save searches and combine them to construct more complicated searches line by line.
Building the search line by line helps you to minimise errors and capture the thought process. The table below shows how to do this.
| Search line | Search strategy | Result will retrieve | ||||
|---|---|---|---|---|---|---|
| 1 | (dog or dogs or bitch* or canine) | references containing keywords: | ||||
| dog | dogs | bitch | ||||
| bitches | canine | |||||
| 2 | (spay* or spey* or neuter* or ovariohysterectom* or ovariectom* or gonadect*) | references containing keywords: | ||||
| spay | spaying | spayed | ||||
| spey | speying | speyed | ||||
| ovariohysterectomy | ovariohysterectomized | ovariohysterectomised | ||||
| ovariohysterectomies | gonadectomy | gonadectomized | ||||
| gonadectomize | gonadectomised | gonadectomise | ||||
| 3 | (mammar* or breast*) | references containing keywords: | ||||
| mammary | mammaries | breast | ||||
| breasts | ||||||
| 4 | (tumour*or tumor* or cancer or cancers or neoplas* or mass or masses or lump or lumps or carcinom*) | references containing keywords: | ||||
| tumour | tumours | tumor | ||||
| tumors | cancer | cancers | ||||
| neoplasm | neoplasms | neoplasia | ||||
| mass | masses | lump | ||||
| lumps | carcinoma | carcinomas | ||||
| Combining the search lines will give you different sets of results | Result will retrieve | |||||
| 1 and 2 and 3 and 4 | will give references containing all the listed keywords concerning neutered dogs with mammary tumours | |||||
| 1 and 2 and 4 | will give references containing all the listed keywords concerning neutered dogs with tumours but not necessarily mammary | |||||
| 1 and 3 and 4 | will give references containing all the listed keywords concerning dogs with mammary tumours but not necessarily those that have been neutered | |||||
| 1 and 2 | will give references containing all the listed keywords concerning neutering and dogs | |||||
| (1 and 2) or (1 and 3 and 4) | will give references on neutering and dogs or dogs with mammary tumours | |||||
Search tools
There are different tools that you can use to help narrow down your search.
Boolean operators
Boolean operators allow you to combine or exclude terms in a search. This will save time and effort by eliminating unsuitable or inappropriate hits from the results.
| Operator | How this works | Example |
|---|---|---|
| AND | both terms need to be in the record before it is returned, it therefore narrows a search | animal AND cruelty |
| OR | either (or both) terms will be in the record, it therefore broadens a search | kidney OR renal |
| NOT | the first term is searched and then any records containing the term after the NOT are excluded, it therefore narrows a search. Care should be taken as it is easy to exclude good records | horse* NOT horseradish |
| Parenthesis | use brackets ( ) to group order of search | dialysis AND (kidney OR renal) |
Other search tools
Most databases and search engines offer other tools that allow you to search more effectively, for example: truncation symbols, wildcards, etc.
The following is a selection of commonly used tools. If they do not work as expected you should check the “help” or “search tips” of the database you are using.
| Tool | How this works | Example |
|---|---|---|
| Phrase searching | use quote marks “ ” to find exact phrases | “foot and mouth” will return results containing the exact phrase “foot and mouth” but not those just containing “foot” or “mouth” |
| Truncation (1) | using an asterisk * at the end of a word will return all words that start with the stem | transplant* will return transplant, transplantation, transplanted, transplanting etc |
| Truncation (2) | using an asterisk * at the beginning of a word will return all words that end with the stem | *glycemia will return hyperglycemia, hypoglycemia |
| Wildcard | use ? in place of a single unknown character use ?? in place of 2 characters | leuk?mia will return leukemia leuk??mia will return leukaemia |
Choosing which databases to search
Once you have defined your search strategy you then need to decide which databases to search.
Research1 shows that the coverage by bibliographic databases of veterinary journals and journals that regularly have veterinary content varies greatly. CAB Abstracts has the highest coverage (90.2%) whilst Medline (PubMed) only has 36.5%.
Therefore to ensure that you retrieve as much of the published evidence on your topic as possible you should use CAB Abstracts and then at least one other database of your choosing. If you only use Medline (PubMed) you risk ignoring 64.5% of all journals with veterinary content. If you only use Google or Google Scholar you will probably get thousands of hits of very little relevance to you.
If you are carrying out a search as part of a review or critical appraisal of available literature for publication you should check if the publisher has minimum requirements for databases searched.
For example a search for a Knowledge Summary for publication in Veterinary Evidence must include CAB Abstracts 1973-current and PubMed as a minimum.
Databases with veterinary coverage
| Name of database | Publisher | Description |
|---|---|---|
| CAB Abstracts | CABI | Applied life sciences database covering veterinary sciences, agriculture, environment, applied economics, food science and nutrition |
| Medline (PubMed) | US National Library of Medicine | Life Sciences database covering biomedicine. Often referred to as PubMed as freely available via the PubMed website. Includes links to full text content from PubMed Central where available. |
| Scopus | Elsevier | Multidisciplinary bibliographic and citation database |
| VetMed Resource | CABI | Veterinary Sciences database containing the bibliographic records from CAB Abstracts, full text documents, specially written reviews etc. |
| Web of Science | Thomson Reuters | Multidisciplinary bibliographic and citation database including Science Citation Index, and other content |
Locating full-text articles
In order to critically appraise the evidence for validity (step 3 of EBVM), you should examine the full-text article rather than relying on the abstract. Reading the abstract may tell you whether an article is relevant but it will not tell you whether the methodology and conclusions are reliable. EBVM Toolkit Numbers 3 through to 15 will show you how to appraise the evidence.
Where can you find the full-text articles?
Is it free?
Some articles can be found free on the web e.g. by searching Pubmed or Google Scholar. Some full-text articles are also available from publishers’ websites and Open Access repositories. However, the majority of veterinary articles are behind paywalls and cannot be accessed without a subscription.
Does your institution or employer provide access?
If you are a member of an academic institution or professional association, you may be able to access full-text articles using their library resources. Additionally, some employers will subscribe to journals on their employees’ behalves.
Do you have an individual subscription?
In some cases you may have a personal subscription to the journal. However, personally subscribing to all relevant journals is costly and likely to be an uneconomical way of practicing EBVM.
Have you tried the RCVS Knowledge Library and Information Service?
Members of RCVS Knowledge Library have access to most veterinary journals, including Veterinary Clinics of North America, JAVMA and Veterinary Surgery, Membership of RCVS Knowledge Library gives you an economical and efficient way of accessing the evidence you need.
If we do not provide access to the article you need, we can usually get it from another library (your academic institution may also provide this service). Even if you’re not a member, RCVS Knowledge Library can provide you with copies of articles at a cheaper rate than most pay-per-article options on publisher websites.
Further guidance
- If you need further help then contact RCVS Knowledge Information Specialists on library@rcvsknowledge.org or 020 7202 0752.
- Literature searching workshops: we offer online workshops on a one-to-one basis covering how to focus a search question, database searching and making the most of our resources. Find out more about our workshops.
- We have a range of online learning courses that provide further guidance for those looking to apply evidence-based principles to their work. Explore our courses on Learn.
Download EBVM Toolkit 2
Read this toolkit in PDF format.
7 pages
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References
- Grindlay, D.et al (2012) Searching the veterinary literature: a comparison of the coverage of veterinary journals by nine bibliographic databases. Journal of Veterinary Medical Education, 39 (4), pp. 404-412. DOI: https://doi.org/10.3138/jvme.1111.109R