Transcript Critical_reading

Critical Reading
VTS 17/10/07
“How to Read a Paper”.
Series of articles by Trisha
Greenhalgh - published in
the BMJ - also available as a
book from BMJ Publications.
How to Read a Paper: The
Basics of Evidence Based
Medicine.
2nd ed. London: BMJ, 2001.
BMJ archive
http://www.bmj.com/cgi/content/full/315/7102/243
http://www.bmj.com/cgi/content/full/315/7104/364
Home page: http://www.bmj.com
Main Points
Many papers published in medical journals have potentially serious
methodological flaws
When deciding whether a paper is valid and relevant to your practice,
first establish what specific clinical question it addressed
Questions to do with drug treatment or other medical interventions
should be addressed by double blind, randomised controlled trials
Questions about prognosis require longitudinal cohort studies, and
those about causation require either cohort or case-control studies
Case reports, though methodologically weak, can be produced rapidly
and have a place in alerting practitioners to adverse drug reactions
The Christopher Centre, University of Valparaiso
http://www.valpo.edu/library/user/read-medpaper.html
The Medline Database
Getting your Bearings (Deciding What the Paper Is About)
Assessing the Methodological Quality of Published Papers
Statistics for the Non-statistician I: Different Types of Data Need Different Tests
Statistics for the Non-statistician II: "Significant" Relations and Their Pitfalls
Papers that Report Drug Trials
Papers that Report Diagnostic or Screening Tests
Papers that Tell You What Things Cost (Economic Analyses)
Papers that Summarize Other Papers (Systematic Reviews and Meta-Analyses)
Papers that Go Beyond Numbers (Qualitative Research)
University of Sheffield
• Core Library for Evidence Based Practice
BBC - Things to Consider when Reading Medical Research
http://www.bbc.co.uk/dna/h2g2/A852761
Where does the new research first appear?
If something is in a peer-reviewed journal it is more likely to be believed than if it
is written up in a non-peer-reviewed journal. To make a decision about a paper,
start off by being very cynical and see if it convinces you. Publication in the BMJ
does not guarantee that it has been well-researched.
Is the experiment well-designed?
If the purpose of the study is to decide whether a particular drug is the best
treatment for a disease, the ideal design is a double blind randomised controlled
trial, where neither the patients nor the researchers know who is on the active
drug.
Problems with double blind controlled trials
If a paper claims to have used a double blind controlled trial, ask if it is really
blind.
Check that they are measuring the right thing.
If you are going to use the results of the study to change things, e.g. changing
treatment, you need to be certain that a treatment is of benefit.
If several different researchers in the past have done several different studies,
they could be analysed together as a meta analysis.
Matched and Unmatched
Make sure that the control is as similar as possible to
the group who are receiving the treatment. One way of
doing this is to match each person in the treatment
group with someone in the control group of similar sex,
age and occupation. If this is possible, better results are
usually obtained.
Case Control Studies
The important thing to consider when reading one of
these papers is ‘Are the controls as similar as possible?'
or are they just the ones it was convenient to access?
How was the research funded?
E.g. drug company research may be more questionable
than independent research.
Reading a paper - READER




Relevant?
Educational? Does it add anything?
Applicable? Primary-care based?
Discrimination - does it answer the questions it
set out to? Any patients excluded? Appropriate
design / statistics? Concepts understood – risk,
NNT, etc?
 Evaluation (oveRall)
“RCT of the READER method of critical appraisal
in general practice” MacAuley et al, BMJ, 1997,
316, 134 (11th April)