Find the best available evidence

Original Editor - Rachael Lowe and the Open Physio project.

Top Contributors - Admin, Rachael Lowe and Kim Jackson  

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

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 obsese 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

Look for secondary sources

1. Guidelines (UK National Library for Health, NICE, SIGN, National Guidelines Clearinghouse; Canadian Medical Association; New Zealand Guidelines Group.)
2. CATs
3. Evidence-based summaries
4. Structured Abstracts
5. Systematic Reviews
6. Online databases (PEDro, Cochrane, CEBP)
7. Search several databases simultaneously use Trip Database
   

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.

• National Guideline Clearinghouse (NGC)
• New Zealand Guidelines Group
• National Institute of Clinical Excellence (NICE) guidelines
• Open Clinical Practice Guidelines
• Australian Clinical Practice Guidelines publications
• Scottish Intercollegiate Guidelines Network (SIGN)
• OpenClinical (Clinical guideline applications for handheld devices)

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.

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 Cochrane Library

The Cochrane Collaboration is an organisation that provides a reliable source of evidence based health information that it publishes in theCochrane 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, a podcast on rehabilitation after lumbar disc surgery.

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.

Look for primary sources

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".

BioMed Central

BioMed Central is an open access online publisher of medical studies, meaning that all of it's content is freely available. The downside is that it's publications are not accredited, only peer-reviewed.

Levels of evidence

This has been adapted from Sackett, Straus and Richardson (2000)

Level of Evidence	Type of Study
1a	Systematic reviews of randomized controlled trials (RCTs)
1b	Individual RCTs with narrow confidence interval
2a	Systematic reviews of cohort studies
2b	Individual cohort studies and low-quality RCTs
3a	Systematic reviews of case-control studies
3b	Case-controlled studies
4	Case series and poor-quality cohort and case-control studies
5	Expert opinion