How to Perform a Simple Literature Search

Introduction

Finding the best evidence requires a systematic and strategic approach. It might be overwhelming at first, but searching literature can be mastered by learning the basic skills. Developing a search strategy starts with identifying the search topic, formulating a question then determining key words. There is a few basic techniques that apply on most databases, however, each one has some differences. It is always helpful to go through help pages of the database you are going to use. You can end up with a great number of results which is time consuming so you need to know how to critically appraise the literature to find the best answer for your preset question^[1].

Where to Start

There are many places to start looking for up to date literature, including hundreds of databases and online journals (some of which can incur a charge for articles and subscriptions; but we want to keep it simple and take a quick initial look to check what evidence is out there. A few great places to start are Cochrane Library, PubMed and Google Scholar. You can also check databases and journals that are physiotherapy-specific such as: PEDro and Journal of Physiotherapy. When you find a paper that is relevant to your search it's helpful to check the reference list for further evidence. Grey literature is another source for searching evidence. Grey Literature refers to data or studies published by government, academic, business and industry sectors but not available commercially. You can search these websites individually or using Google's advanced search to further narrow your search results^[1].

Formulating the Question

There are two methods that you can use to formulate search questions: PICO Method:

P - Population / Problem
I - Intervention / Indicator
C - Comparator
O - Outcome

6Ws Method:

What?
Who?
Which?
Where?
When?
Why?
How?

Identifying Key Words

For a quick search you can only pick 2 or 3 key words that will help us narrow down our search. For example: I want to know; How effective are eccentric exercises in treating Achilles Tendinopathy? If we put the whole question into the search engine this gives us 35 results - A manageable number of papers to look through but of which 14 potentially are not completely relevant to our question. So we pick the key words: Achilles Tendinopathy and Eccentric Exercise If we put this term into PubMed this gives us 140 results (at time of writing this page). A little too many to look through for a quick search. So we can apply some very simple constraints to our search to help us narrow down the number of papers but also keep the results relevant to our question:

Boolean Searches

When you rely on specific modifiers to do a search. This will help you find the closest results to the key words/ phrases you are looking for. You can include the following modifiers in your search: quotes, parenthesis, AND, OR and NOT You can use these terms in between your key words to make your search more specific. They must be in CAPITAL LETTERS!

AND	"Achilles Tendinopathy" AND "Eccentric Exercise"	Will bring up everything in the search with both Achilles Tendinopathy and Eccentric Exercise. If you do not put the AND, the search engine will automatically assume that there is an AND between the words.
OR	"Achilles Tendinopathy" OR "Eccentric Exercise"	This search gives us 691 results on PubMed. These papers include just Eccentric Exercise or just Achilles Tendinopathy . This is also useful if we want to search for something which has more than 1 name like Physiotherapy and Physical Therapy. The search will bring up all articles with either "Physiotherapy" OR "Physical Therapy"
NOT	"Achilles Tendinopathy"NOT "Achilles rupture"	If you want to exclude a certain term from your search you can use the word NOT just before the term. This means that your search results will exclude any article containing that term.

Quotation marks ("speech marks")

If you are searching for an exact phrase, like "Achilles Tendinopathy" you can put the phrase in quotation marks to group the words together. This will allow a search to be performed with the words in the exact order you typed them. You can use the quotation marks in addition to other modifiers. If we enter Achilles Tendinopathy (without quotation marks) into the search engine, PubMed will automatically link the words using AND, which isn't what we want (Achilles AND Tendinopathy). We want to use the term as a phrase to allow PubMed to search for the words linked together, so we use "Achilles Tendinopathy". The same again for Eccentric Exercise, we want to search for this together as a phrase "Eccentric Exercise". When you apply this together "Achilles Tendinopathy" AND "Eccentric Exercise" PubMED will give you 44 results of which are all relevant. Now go and have a go. Remember each database or search engine can be a little bit different so be sure to check out the help page.

Parentheses/ Nesting ( )

If you want to do a complex search you can combine terms and modifiers. The parentheses enables the search engine to search for certain phrases/terms first, thus the term 'nesting' is used.

You will use parentheses to group phrases joined by OR, when another Boolean operator is used in the same search. "Achilles Tendinopathy" AND "eccentric exercise" AND (physiotherapy OR "physical therapy") Thus the results will have the first two phrases somewhere in the article, and either physiotherapy or physical therapy.

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Limiters/Filters

Limit by date, gender, language, articles that include an abstract, etc. You can specify a full text search or limit to a search of abstract and title.

Truncation and Wildcards

Truncation can be applied to identify all possible endings, for example: pharm* will identify pharmacology, pharmacy, pharmaceutical. Wildcards are used to identify different spelling and plurals, for example: behavio?r, wom?n. Not all databases use truncation and wildcards so it's helpful to check their help pages before using these constraints.

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