Find the best available evidence

Original Editor - Rachael Lowe and the Open Physio project.

Top Contributors - Rachael Lowe  

Related Pages

  1. Evidence Based Practice (EBP)
  2. Step1: Formulate an answerable question
  3. Step 2: Find the best available evidence
  4. Step 3: Appraise the evidence
  5. Step 4: Implement the evidence
  6. Step 5: Evaluate the outcome

Introduction

Finding the evidence is the second step in the five steps of evidence-based practice. 

It is important when searching for evidence that search terms are referred back to your original PICO question. The process of finding evidence therefore follow three key steps:

  1. Identify terms to fit your PICO question
  2. Look for secondary sources
  3. Search for primary sources

Identify terms to fit your PICO question

To make your search as efficient as possible, it is a good idea to understand some of the basic principles of effective searching, which are:

  1. Carefully define your clinical question (you should have done this in step 1).
  2. Choose your key search terms.
  3. Broaden your search if necessary, with synonyms, truncation and/or wildcards.
  4. Use Boolean operators.

Consider your PICO question and convert this into a search strategy.  To do this, you should do three things:

  1. Underline the key terms – those most specific to your question
  2. Number the PICO elements in order of importance from 1-4
  3. Think of alternate spellings, synonyms and truncations

Example

Scenario: A 64 year old obese male who has tried many ways to lose weight presents with a newspaper article about ‘fat-blazer’ (chitosan). He asks for your advice.

Your question in PICO format might be:

Population/problem obese patients
Intervention/indicator chitosan
Comparator placebo
Outcome decrease weight

Question: In obese patients, does chitosan, compared to a placebo, decrease weight.

After converting into a search strategy you might end up with this:

Population/problem obese OR overweight (2)
Intervention/indicator chitosan (1)
Comparator placebo (4)
Outcome decrease weight OR kilogram* (3)

NOTE: ‘*’ is a truncation symbol that means further letters can be added to the word
OR finds studies containing either of the specified words/phrases, and broadens your search
AND finds studies containing both specified words/phrases, and narrows your search

Use these search terms to look for primary and secondary sources.

This mini tutorial shows you how to convert your search question into a search strategy that will work on any bibliographic database.


Look for secondary sources

  1. Guidelines (NICE, SIGN, National Guidelines ClearinghouseNew Zealand Guidelines GroupOpen Clinical Practice GuidelinesAustralian Clinical Practice Guidelines.)
  2. CATs (CAT Crawler)
  3. Online databases (Bandolier, Clinical Evidence, EBM Online, ACP Journal Club, Cochrane Library)
  4. Online databases specific to physiotherapy (PEDro, CEBP)
  5. Search several databases simultaneously use Trip Database
  6. Knowledge translation tools.

Clinical guidelines

Traditionally, clinical guidelines have been viewed with suspicion by anyone interested in working from the evidence base, as "guidelines" were often little more than one individual's personal opinion. Over the past 5 years however, the approach to producing clinical guidelines has radically changed, with vast amounts of time and resources being poured into their development.

A clinical guideline focuses on the current understanding of a particular condition and makes use of a diverse range of academic literature to establish an approach to best practices, based on the outcomes of a large number of the studies available. They also inform the reader what level of evidence has been used to establish "best practice", from systematic reviews of the literature (Level A) to expert clinical opinion (Level D). This allows the clinician to make up their own mind about how solid is the foundation upon which the guideline is built and how much weight to allocate it.

A few of the organisations responsible for developing guidelines are presented below (in no particular order). Since different organisations are tasked with developing different guidelines, you might have to look around until you find what you're looking for. It should also be borne in mind that not only are new guidelines being developed all the time but old ones are typically reviewed every 2-3 years, so it's always useful to ensure you have the latest version.

CATs

A critically appraised topic (or CAT) is a short summary of evidence on a topic of interest, usually focussed around a clinical question. Defined as a brief “summary of a search and critical appraisal of the literature related to a focused clinical question, which should be kept in an easily accessible place so that it can be used to help make clinical decisions”[1]. A CAT is like a shorter and less rigorous version of a systematic review, summarising the best available research evidence on a topic. Usually more than one study is included in a CAT. When professionals summarise a single study, the outcome is a critically appraised paper (or CAP). CATs and CAPs are one way for busy clinicians to collate and share their appraisals.

Read more about CATs

Online databases

There are an increasingly large number of online databases that serve as useful resources for both practising physiotherapists and students. They have content from a wide variety of journals, which saves researchers the sometimes painful job of trawling through individual publications. The following list is not comprehensive.

The Cochrane Library

The Cochrane Collaboration is an organisation that provides a reliable source of evidence based health information that it publishes in the Cochrane Library. From their website, "It includes reliable evidence from Cochrane and other systematic reviews, clinical trials, and more. Cochrane reviews bring you the combined results of the world’s best medical research studies". The Cochrane Library also publishes podcasts, which are mostly medical in nature but which also contain content relevant for physiotherapists. For example,podcast on rehabilitation after lumbar disc surgery.

Online databases specific to physiotherapy

PEDro

The Physiotherapy Evidence Database is an initiative of the Centre for Evidence-Based Physiotherapy (CEBP) and was developed "...to give rapid access to bibliographic details and abstracts of randomised controlled trials, systematic reviews and evidence-based clinical practice guidelines in physiotherapy". For randomized controlled trials (RCT), PEDro rates studies on a 0-11 scale (a higher number is better). The links page on PEDro contains links to other useful resources for anyone interested in exploring the evidence base in health-related literature.

The Centre for Evidence Based Physiotherapy (CEBP)

The Centre for Evidence Based Physiotherapy has a "...mission is to search, collect and disseminate available scientific evidence in the physiotherapy domain for physiotherapists, health care workers, patients and financiers of health care". All of the papers on it's website are freely available.

Knowledge translation tools

Physiopedia is a resource that gathers the evidence and creates useable information that aids the knowledge transfer process.

Many research groups are also now collating thier evidence into user friendly tools to assist the transfger of research evidence into practice.  Two groups doing this that have published their knowledge transfer tools in Physiopedia are lead by Alison Hoens and Anita Gross:


Look for primary sources

A number of searchable databases exist, including MEDLINE, CINAHL and PubMed. Search strategies entail using 1 or more key words that may be found in the article’s title or abstract.

Use methodological filters to target the right type of study. For instance, PubMED filters for:

  • therapy
  • diagnosis
  • prognosis
  • aetiology

PubMed

Pubmed "...is a service of the US National Library of Medicine that includes over 18 million citations from MEDLINE and other life science journals for biomedical articles back to the 1950s. It also includes links to full text articles and other related resources".

This PubMed demonstration is very useful:



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References

  1. Centre for Evidence Based Emergency Medicine, http://www.ebem.org/definitions.html#Critically%20appraised%20topic last accessed 21st March 2011