Locating studies for your systematic review

Ruth Mitchelland Gail Higgins

What are we trying to achieve?

● Up-to-date, relevant, unbiased systematic reviews of the effects of interventions for particular health care problems

How do we achieve this?

● Locate all possible randomised controlled trials of interventions for these health care problems

Locating all possible RCTs

● Sources◆ electronic databases◆ handsearching◆ reference lists◆ personal communication

Use a strategic approach

● Start at highest yield source and work down● Electronic databases

◆ Cochrane Review Group register◆ Cochrane Controlled Trials Register◆ MEDLINE◆ EMBASE◆ Other appropriate databases

● Handsearching (reference lists, conference proceedings)

● Personal communication

Minimise bias

● Sources of bias◆ language◆ source (which journal, database etc)◆ publication status (full article, conference

abstract, unpublished etc)

Designing a search strategy

● Two-stage process:

◆ Formulate your question

◆ Identify your key concepts

Formulate your question● Translate the clinical problem into a

structured question and identify key concepts

e.g. Is cannabis effective in treating pain?

Standard Rx or placebo

CannabisPainComparisonInterventionClinical Problem

Identify your search terms (i)● Select database e.g. MEDLINE, and

identify the subject headings that match your key concepts

Standard Rx or placebo

CannabisPainComparisonInterventionClinical Problem

Identify your search terms (ii)

● Use “text words” for

◆ synonyms – e.g. bed sore (decubitus ulcer)

◆ spelling – e.g. fetal (foetal)– marijuana or marihuana

Identify your search terms (iii)

● Add the type of study you want ◆ e.g. randomised controlled trial

● For Cochrane systematic reviews ◆ use the Cochrane highly sensitive search

strategy for randomised controlled trials in MEDLINE

RandomisedControlled Trials

Cochrane SearchStrategy506,604

Pain(MeSH headings

OR text words)

201,806

Cannabis(MeSH headings

ORtext words)

10,507

ANDAND

AND

31

Tips for saving time and effort

● Look at the terms used in citations you know are relevant

● Add search terms to your strategy, use on part of a database, and see what you get back

● Don’t search before an intervention was invented

● Get up-to-date advice from someone who knows

When do we stop searching?

● No right answer, be guided by◆ The return you’re getting◆ Resources◆ Time constraints

Documenting your search● Important so you can remember what

you’ve done● Important for users of your review● Document

◆ what you searched ◆ when you searched ◆ how you searched

Anticoagulants for heart failure in sinus rhythm

Managing references

● Use specialised software e.g. ProCite, EndNote, IdeaList, Reference Manager

◆ saves typing ◆ reduces transcription errors◆ helps identify duplicates◆ helps keep track of studies

Don’t be shy – ask for help!

● Retrieving studies is not simple● Ask your Collaborative Review Group’s

Trials Search Coordinator for advice● Section 5 of the Reviewers’ Handbook● Medical librarians