Making Sense of Critical Appraisal

225 Pages·2002·1.31 MB·English

by  Ajetunmobi

Making Sense of
Critical Appraisal
To Ireti Oredola…
Making Sense of
Critical Appraisal
O. AjetunmobiMB BS MRCPSYCH
Specialist Registrar in General Psychiatry,
Towers Hospital, Leicester
Hodder Arnold
AMEMBER OF THE HODDER HEADLINE GROUP
First published in Great Britain in 2002 by
Hodder Arnold a member of the Hodder Headline Group,
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© 2002 O Ajetunmobi
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Acatalog record for this book is available from the Library of Congress
ISBN-10: 0 340 80812 8
ISBN-13: 978 0 340 80812 2
2 3 4 5 6 7 8 9 10
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Contents
Introduction vii
Chapter 1 Basic stats 1
Chapter 2 Relevant study design issues 58
Chapter 3 Critical appraisal of studies on diagnostic tests 69
Chapter 4 Critical appraisal of cross-sectional surveys 85
Chapter 5 Critical appraisal of prospective studies 100
Chapter 6 Critical appraisal of retrospective studies 112
Chapter 7 Critical appraisal of randomized clinical trials 122
Chapter 8 Handling survival time data 146
Chapter 9 Critical appraisal of systematic reviews 154
Chapter 10 Critical appraisal of clinical audit 166
Chapter 11 Critical appraisal of economic evaluations 168
Chapter 12 Critical appraisal of qualitative studies 190
Glossary of terms 203
References and suggested further reading 206
Index 209
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Introduction
In keeping with the ethos of evidence-based medical practice, critical
appraisal of research papers has been introduced into the examination
curricula of both undergraduate and postgraduate medical programmes
alike. These new kinds of examinations are designed to test candidates’
ability to critique the quality of evidence presented in research papers
for clinical relevance.
Although many helpful courses and workshops do exist, it is a gener-
ally shared feeling among examinees and trainers alike that being a
relatively new entity, the scope of critical appraisal as a subject remains
somewhat unclear. To further muddy the waters, few concise texts
geared towards examinations on critical appraisal exist to date, render-
ing exam preparation a tedious task in already unchartered territory.
Unsurprisingly, therefore, some candidates approach this aspect of their
examinations with an understandable degree of trepidation.
Ironically, once mastered, critical appraisal examinations represent an
area in which candidates can score highly with a relatively high degree
of certainty. This is less the case for essay or multiple-choice papers,
never mind clinical examinations.
My intention in writing this book was to provide candidates with
an easy-to-use exam-oriented text that covers most aspects of critical
appraisal. Concepts are presented in a user-friendly format, particularly
for the benefit of those who, like myself, find epidemiological and stat-
istical concepts rather migraine-inducing.
Examinations apart, this book would also be a handy resource for all
doctors and other professionals seeking to improve their skills at under-
standing and evaluating clinical research papers.
The first chapter deals with relevant aspects of general statistics and
study design. This provides a solid basis for approaching the other
chapters, which have been deliberately organized according to the
types of studies that may be presented in research papers.
Chapters on economic analyses, qualitative research principles and
clinical audit have been included, and the book also contains a glossary
of epidemiological and statistical terms and definitions.
For the sake of clarity, fictitious research scenarios are presented
alongside the main text where appropriate.
Enjoy!
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Basic stats
1
Introduction 1
Descriptive statistics 2
Hypothesis testing and statistical inference 11
Estimation 19
Statistical tests 26
Correlation and regression 32
Non-essential information 43
Introduction
Critical appraisal is concerned with the acquisition of necessary skills
with which to discern clinical research papers accurately. Although it is
only natural that some degree of overlap does exist between the two
subjects, critical appraisal should not really be regarded as just another
aspect of medical statistics. This misconception often leads to an over-
estimation of the level of statistical knowledge required for critical
appraisal.
In this chapter, only the statistical concepts that are relevant to the
purposes of critical appraisal are discussed. These concepts are care-
fully presented in a gentle step-by-step approach with aid of ‘easily
understandable’ vignettes as necessary.
A separate ‘Non-essential information’ section is included for the
more adventurous reader who may also want to consult more formal
statistical texts for a more in-depth treatment of the various statistical
concepts discussed.