Critical Appriasal eBook (Preview)

- 1 -

- 2 - Critical Appraisal 

FRCEM FINAL 

Critical Appraisal 

“Made Easy” 

Moussa Issa 

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DISCLAIMER 

i 

DISCLAIMER 

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Reprinted with Revisions 2020 

ISBN-13: 978-1999957551 

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Authored by Moussa Issa 

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ii 

Critical Appraisal 

PREFACE 

Nowadays, the amount of health care research undertaken has grown significantly, 

especially over the past decades. 

Each year, hundreds of published Medical journals contain thousands of reports of 

research studies. 

Surprisingly, it is an unfortunate fact that not all published research is good 

quality. The health care professional has to search the literature for information 

on factors affecting patient care and/or service delivery. These articles will vary in 

terms of quality, comprehensibility and relevance to practice. Some studies, 

although well researched, will have limitations due to aspects of research design. 

This small compilation provides prospective candidates a glossary of medical terms 

used in Evidence Based-Medicine and a step-by-step approach on how to critically 

appraise articles published in Medical journals and guidelines on how to search for 

reports. 

The purpose of critical appraisal is to help the health care professional to read 

research studies objectively by identifying valid and irrelevant points, the strengths 

and weaknesses and the usefulness of a report with its limitations. 

Critical reading of research reports increases the practitioner's understanding of 

the research process. Doctors undertaking their own studies will eventually benefit 

from developing their critical evaluation skills by appraising their own projects and 

enhance their skills at all stages of the study process from project design to writing 

the final report. 

Readers will be guided through the processes and provided with information on 

the factors that can affect the quality of the literature search and the study articles 

found. Exercises and past exams are inserted to reinforce the candidate's 

understanding of the text. 

Dr Muhammad Fayyaz Alam Janjua 

MBBS MRCP (UK) MRCPI Bsc 

Medical Registrar

ACKNOWLEDGEMENTS 

iii 

ACKNOWLEDGEMENTS 

To my wife and children: Marlene, Tatiana, Kevin, Ryan and Brandon. I thank you for your love 

and support. You’ve always been by my side and never complained watching me working on 

my books when you needed me the most. 

To my co-Editors: Tina Cardoza, Muhammad Amjad, Faizan Alam and Nasir Mahmood. Thank 

you for taking the time to lay this out and providing me the inspiration to do this. Muhammad 

Amjad you are an amazing colleague, a kind brother and a great friend; thank you and I 

appreciate you more than you’ll ever know. 

To some other important people: Sayed Ramadan, Zain Ul Abadin, Russel Hall, Robyn 

Pretorius, Rana Tanweer, Moez Ibrahim, Mohanad Ibrahim, Yasser Mohamad, Awwad El 

Mahdi, Luke Joseph Chirayil, Donna Edano, Abubakar Bin Omer Badam, Pintu Syed, and all the 

others who took the time to help me find some needed corrections to my books that only 

made this workbook and latest printing even better. I would like to thank you for your interest 

in my work and I encourage you to continue to send me your invaluable feedback and ideas 

for further improvement of the FRCEM Exam book series. I am grateful to you. 

To all my clients and Colleagues: Your continued patronage has helped me keep this book 

running. For this, I never mind the arthritis on my writing hand. We have ventured many roads 

together, some new and some well-travelled, but we have continued to sharpen each other 

with patience, perception and perseverance. The pain cannot overcome the happiness that I 

am feeling right now, thanks to you. 

To you: The only thing that can stop you from showing the best results is you being so 

extremely nervous. There’s no need to be scared, buddy. You are ready to show everyone that 

you are the smartest fella in the world! Good luck! 

I feel blessed that social media have given me the chance to reconnect or stay connected with 

many colleagues all over the world. I am grateful to you all and wish you success throughout 

your exams. Remember, few years ago, I was also at the beginning like you, with little effort 

and perseverance, I managed to clear all FRCEM Exams. 

An exam is not a game. It’s a background for your future. 

Wish you to pass all exams. 

Dr Moussa Issa 

MBChB MRCEM FRCEM 

My sources: 

Disclaimer: Information and images included in these notes originate from multiples sources 

such as academic journals, textbooks, published articles, Emergency Medicine websites and 

Blogs etc. The Editor and the Publisher have gone to every effort to seek permission from and 

acknowledge the sources of clinical guidelines and images which appear in this compilation 

that is public on the internet. Nevertheless, should there be any cases where Copyright 

holders have not been identified or suitably acknowledged, the author welcome advice from 

such Copyright holders and will endeavor to amend the text accordingly on future prints.

TABLE OF CONTENTS 

1 


1. BASIC OF EVIDENCE BASED MEDICINE ___________________ 1 

I. Introduction to Critical Appraisal ____________________________________________ 1 

1. EVIDENCE BASED MEDICINE _________________________________________________________ 1 

2. CRITICAL APPRAISAL _______________________________________________________________ 1 

3. HIERARCHY OF EVIDENCE ___________________________________________________________ 1 

4. PROS OF CRITICAL APPRAISAL IN PRACTICE _____________________________________________ 2 

II. Concepts & Definitions ____________________________________________________ 3 

ALLOCATION CONCEALMENT __________________________________________________________ 3 

ACCURACY _________________________________________________________________________ 3 

BLINDING __________________________________________________________________________ 3 

CHANCE, BIAS AND CONFOUNDING _____________________________________________________ 4 

CLINICAL PREDICTION RULE_____________________________________Error! Bookmark not defined. 

CONSORT STATEMENT ________________________________________Error! Bookmark not defined. 

CONVENIENCE SAMPLING ______________________________________Error! Bookmark not defined. 

COX PROPORTIONAL-HAZARD MODEL ____________________________Error! Bookmark not defined. 

EFFECT MODELS ______________________________________________Error! Bookmark not defined. 

EFFICACY AND EFFECTIVENESS __________________________________Error! Bookmark not defined. 

ENDPOINTS OR OUTCOMES ____________________________________Error! Bookmark not defined. 

FACTORIAL DESIGN ___________________________________________Error! Bookmark not defined. 

GRADE OF RECOMMENDATION _________________________________Error! Bookmark not defined. 

HETEROGENEITY _____________________________________________Error! Bookmark not defined. 

HYPOTHESIS _________________________________________________Error! Bookmark not defined. 

INTENTION TO TREAT ANALYSIS _________________________________Error! Bookmark not defined. 

INTEROBSERVER VARIABILITY ___________________________________Error! Bookmark not defined. 

INTRAOBSERVER VARIABILITY ___________________________________Error! Bookmark not defined. 

JADAD _____________________________________________________Error! Bookmark not defined. 

HAZARD (OR HAZARD RATE) ____________________________________Error! Bookmark not defined. 

HAZARD RATIO _______________________________________________Error! Bookmark not defined. 

KAPLAN-MEIER CURVE ________________________________________Error! Bookmark not defined. 

KAPPA _____________________________________________________Error! Bookmark not defined. 

LEVEL OF EVIDENCE ___________________________________________Error! Bookmark not defined. 

LIKELIHOOD RATIOS ___________________________________________Error! Bookmark not defined. 

METAREGRESSION ____________________________________________Error! Bookmark not defined. 

MULTIVARIATE ANALYSIS ______________________________________Error! Bookmark not defined. 

ODD RATIO __________________________________________________Error! Bookmark not defined. 

PRE-TEST ODDS ______________________________________________Error! Bookmark not defined. 

POST-TEST ODDS _____________________________________________Error! Bookmark not defined. 

PRE-TEST PROBABILITY ________________________________________Error! Bookmark not defined. 

POST-TEST PROBABILITY _______________________________________Error! Bookmark not defined. 

POWER _____________________________________________________Error! Bookmark not defined. 

PRAGMATIC & EXPLANATORY RESEARCH __________________________Error! Bookmark not defined. 

PRECISION __________________________________________________Error! Bookmark not defined. 

RANDOMISATION ____________________________________________Error! Bookmark not defined. 

RECEIVER OPERATOR CURVE (ROC)_______________________________Error! Bookmark not defined. 

REGRESSION________________________________________________________________________ 6 

RISK REDUCTION ____________________________________________________________________ 6 

RELIABILITY ________________________________________________________________________ 7 

SENSITIVITY (TRUE POSITIVES) _________________________________________________________ 7 

SENSITIVITY ANALYSIS _________________________________________Error! Bookmark not defined. 

SPECIFICITY (TRUE NEGATIVES) __________________________________Error! Bookmark not defined. 

SURVIVAL ANALYSIS ___________________________________________Error! Bookmark not defined. 

SYSTEMATIC REVIEW __________________________________________Error! Bookmark not defined. 

TYPE 1ERROR ________________________________________________Error! Bookmark not defined. 

TYPE 2 ERROR _______________________________________________Error! Bookmark not defined. 

VALIDATION AND DERIVATION PROCEDURES _______________________Error! Bookmark not defined. 

VALIDITY AND GENERALISABILITY ________________________________Error! Bookmark not defined. 

III. Evidence Hierarchy _______________________________________________________ 9 

HIERARCHIES OF EVIDENCE _____________________________________Error! Bookmark not defined. 

LEVELS OF EVIDENCE GRADE - EVIDENCE GRADES ___________________Error! Bookmark not defined. 

Moussa Issa | www.moussaissabooks.com |

2 FRCEM Final Critical Appraisal 

1. CASE SERIES & CASE REPORTS ________________________________ Error! Bookmark not defined. 

2. CROSS SECTIONAL STUDY____________________________________ Error! Bookmark not defined. 

3. CASE CONTROL STUDIES ____________________________________ Error! Bookmark not defined. 

4. COHORT STUDIES __________________________________________ Error! Bookmark not defined. 

5. RANDOMISED CONTROLLED STUDIES __________________________ Error! Bookmark not defined. 

6. SYSTEMATIC REVIEW _______________________________________ Error! Bookmark not defined. 

7. META-ANALYSIS __________________________________________________________________ 10 

IV. Study Design ____________________________________ Error! Bookmark not defined. 

INTRODUCTION _____________________________________________ Error! Bookmark not defined. 

1. QUANTITATIVE STUDIES _____________________________________ Error! Bookmark not defined. 

2. OBSERVATIONAL STUDIES ___________________________________ Error! Bookmark not defined. 

3. INTERVENTIONAL STUDIES ___________________________________ Error! Bookmark not defined. 

V. Randomisation in Clinical Trial ______________________ Error! Bookmark not defined. 

1. RANDOM NUMBER GENERATION _____________________________ Error! Bookmark not defined. 

2. RANDOMISATION METHODS _________________________________ Error! Bookmark not defined. 

3. CONCEALED ALLOCATION ___________________________________ Error! Bookmark not defined. 

VI. Sampling in Clinical Trial ___________________________ Error! Bookmark not defined. 

SAMPLE SIZE ________________________________________________ Error! Bookmark not defined. 

SIMPLE RANDOM SAMPLING ___________________________________ Error! Bookmark not defined. 

SYSTEMATIC SAMPLING _______________________________________ Error! Bookmark not defined. 

CLUSTER SAMPLING __________________________________________ Error! Bookmark not defined. 

CONVENIENCE SAMPLING _____________________________________ Error! Bookmark not defined. 

VII. Statistics _______________________________________ Error! Bookmark not defined. 

1. HYPOTHESIS TESTING (THE P-VALUE) __________________________ Error! Bookmark not defined. 

2. ESTIMATION (CONFIDENCE INTERVALS) ________________________ Error! Bookmark not defined. 

3. TYPE I & TYPE II STATISTICAL ERRORS __________________________ Error! Bookmark not defined. 

4. POWER __________________________________________________ Error! Bookmark not defined. 

5. EXPERIMENTAL EVENT RATE (EER) ____________________________ Error! Bookmark not defined. 

6. CONTROL EVENT RATE (CER) _________________________________ Error! Bookmark not defined. 

7. ABSOLUTE RISK ____________________________________________ Error! Bookmark not defined. 

8. RELATIVE RISK_____________________________________________ Error! Bookmark not defined. 

9. ODDS RATIO ______________________________________________ Error! Bookmark not defined. 

10. RISK REDUCTION _________________________________________ Error! Bookmark not defined. 

11. NUMBER NEEDED TO TREAT (NNT) ___________________________ Error! Bookmark not defined. 

12. NUMBER NEEDED TO HARM (NNH) ___________________________ Error! Bookmark not defined. 

13. KAPPA __________________________________________________ Error! Bookmark not defined. 

VIII. Normal & Skewed Distributions ___________________ Error! Bookmark not defined. 

I. TYPES OF DATA IN MEDICAL RESEARCH _________________________ Error! Bookmark not defined. 

II. NORMAL OR GAUSSIAN DISTRIBUTION _________________________ Error! Bookmark not defined. 

III. SKEWED DISTRIBUTION _____________________________________ Error! Bookmark not defined. 

IV. MEASURES OF CENTRAL TENDENCY ___________________________ Error! Bookmark not defined. 

V. TYPES OF OUTCOMES IN CLINICAL RESEARCH____________________ Error! Bookmark not defined. 

2. CRITICAL APPRAISAL APPROACH ______________________ 13 

1. INTRODUCTION OR BACKGROUND ____________________________ Error! Bookmark not defined. 

2. METHODS ________________________________________________ Error! Bookmark not defined. 

3. RESULTS _________________________________________________ Error! Bookmark not defined. 

4. DISCUSSIONS OR CONCLUSIONS ______________________________ Error! Bookmark not defined. 

5. MISCELLANEOUS OBSERVATIONS _____________________________ Error! Bookmark not defined. 

6. CONSORT STATEMENT ______________________________________ Error! Bookmark not defined. 

II. Appraising Randomised Controlled Trials ______________ Error! Bookmark not defined. 

12 QUESTIONS TO HELP YOU MAKE SENSE OF A TRIAL (Adapted from Guyatt et al) __ Error! Bookmark 

not defined. 

SECTION A: ARE THE RESULTS OF THE STUDY VALID? ________________ Error! Bookmark not defined. 

SECTION B: WHAT ARE THE RESULTS? ____________________________ Error! Bookmark not defined. 

SECTION C: WILL THE RESULTS HELP LOCALLY? _____________________ Error! Bookmark not defined. 

III. What is Therapeutic study? ______________________________________________ 14 

INTRODUCTION ____________________________________________________________________ 14 

Disclaimer: Information and images included in these notes originate from multiples sources such as academic journals, textbooks, published articles, Emergency 

Medicine websites and Blogs etc. The Editor and the Publisher have gone to every effort to seek permission from and acknowledge the sources of clinical guidelines and 

images which appear in this compilation that is public on the internet. Nevertheless, should there be any cases where Copyright holders have not been identified or 

suitably acknowledged, the author welcome advice from such Copyright holders and will endeavor to amend the text accordingly on future prints.


3 

1. SELECTION AND ALLOCATION OF STUDY PARTICIPANTS __________________________________ 14 

2. RANDOMISATION __________________________________________Error! Bookmark not defined. 

3. ALLOCATION CONCEALMENT _________________________________Error! Bookmark not defined. 

4. BLINDING _________________________________________________Error! Bookmark not defined. 

5. INTENTION TO TREAT ANALYSIS _______________________________Error! Bookmark not defined. 

6. FOLLOW-UP _______________________________________________Error! Bookmark not defined. 

7. OUTCOME MEASURES _______________________________________Error! Bookmark not defined. 

8. MEASURES OF EFFECTIVENESS ________________________________Error! Bookmark not defined. 

IV. Appraising Therapeutic Studies ____________________________________________ 15 

SECTION A. DOES THIS STUDY ADDRESS A CLEAR QUESTION? ________________________________ 15 

SECTION B. ARE THE RESULTS OF THIS SINGLE TRIAL VALID? _________________________________ 15 

SECTION C. WHAT WERE THE RESULTS? _________________________________________________ 15 

SECTION D. CAN I APPLY THESE VALID, IMPORTANT RESULTS TO MY PATIENT? ___ Error! Bookmark not 

defined. 

V. What is Diagnostic Test study? _____________________________________________ 16 

1. TERMS USED IN REPORTING DIAGNOSTIC TEST DATA ____________________________________ 16 

2. HOW ARE THE TERMS USED? _________________________________Error! Bookmark not defined. 

3. LIKELIHOOD RATIOS _________________________________________Error! Bookmark not defined. 

4. THE REFERENCE STANDARD (GOLD STANDARD) ___________________Error! Bookmark not defined. 

VI. Appraising Diagnostic Test Studies _________________________________________ 17 

SECTION A. HOW DO WE ASSESS IF A DIAGNOSTIC TEST STUDY IS VALID? Error! Bookmark not defined. 

SECTION B. HOW DO WE ASSESS THE RESULTS OF THE TEST? __________Error! Bookmark not defined. 

SECTION C. HOW TO APPLY THE DIAGNOSTIC TEST TO A SPECIFIC PATIENT ______ Error! Bookmark not 

defined. 

THE ROC CURVE ______________________________________________Error! Bookmark not defined. 

VII. Appraising a Systematic Review ___________________________________________ 18 

TEN QUESTIONS TO HELP YOU MAKE SENSE OF A SYSTEMATIC REVIEW __Error! Bookmark not defined. 

VIII. Appraising Cohort Studies _______________________________________________ 20 

12 QUESTIONS TO HELP YOU MAKE SENSE OF COHORT STUDY _________Error! Bookmark not defined. 

IX. Appraising Case Control Studies ___________________________________________ 21 

11 QUESTIONS TO HELP YOU MAKE SENSE OF CASE CONTROL STUDY _________________________ 21 

X. Appraising Qualitative Research ___________________________________________ 22 

10 QUESTIONS TO HELP YOU MAKE SENSE OF QUALITATIVE RESEARCH ________________________ 22 

XI. Appraising Economic Evaluations __________________________________________ 23 

12 QUESTIONS TO HELP YOU MAKE SENSE OF ECONOMIC EVALUATIONS ______________________ 23 

3. COMMONLY ASKED QUESTIONS ______________________ 24 

QUESTIONS 1 ______________________________________________________________________ 24 

QUESTION 2 _________________________________________________Error! Bookmark not defined. 

QUESTION 3 _______________________________________________________________________ 25 

INDEX ______________________________________________ 26 

REFERENCES _________________________________________ 30 


1. BASIC OF EVIDENCE BASED MEDICINE 

1 

1. BASIC OF EVIDENCE 

BASED MEDICINE 

I. Introduction to Critical 

Appraisal 

1. EVIDENCE BASED MEDICINE 

• Evidence based medicine (EBM) is defined as ‘the integration of best 

research evidence with clinical expertise and patient values’ 1 . 

• This is a process of life-long self-directed learning and allows the 

integration of good quality published literature with clinical expertise 

and the opinions and values of patients and their families or carers 2 . 

• EBM is important to improving the quality of patient care, as it 

contributes to identifying those interventions that work and the 

elimination of those that are ineffective or do not work 

2. CRITICAL APPRAISAL 

• Critical appraisal is the process of systematically examining research 

evidence to assess its validity, results and relevance before using it to 

inform a decision. 

• Critical appraisal is an essential part of evidence-based clinical 

practice that includes the process of systematically finding, 

appraising and acting on evidence of effectiveness. 

• Critical appraisal allows us to make sense of research evidence and 

thus begins to close the gap between research and practice. 

3. HIERARCHY OF EVIDENCE 

• The hierarchy has an order, advancing from the simple case studies 

and opinions, literature reviews through to more advanced 

methodologies such as the randomised controlled trial (RCT), 

systematic reviews and meta-analysis. 

• The RCT is considered the gold standard for evaluating the 

effectiveness of interventions. 



• It is defined as a quantitative, comparative, controlled experiment in 

which a group of investigators study two or more interventions in a 

series of individuals who receive them in a random order 3 while the 

intention is to make the research objective, the results will only really 

apply to the limits set within the trial or to the specific population 

being studied 4 . 

• Systematic reviews are particularly useful because they usually 

contain an explicit statement of the objectives, materials and 

methods, and should be conducted according to explicit and 

reproducible methodology. 

• Randomised controlled trials and systematic reviews are not 

automatically of good quality and should be appraised critically. 

• Critical appraisal is one step in the process of evidence-based clinical 

practice. Most research is not perfect, and critical appraisal is not an 

exact science it will not give us the right answer. But it can help us to 

decide whether we think a reported piece of research is good enough 

to be used in decision making. 

• There are many factors that come into play when making healthcare 

decisions research evidence is just one of them. If research has flaws, 

it is up to readers to use their critical appraisal skills to decide 

whether this affects the usefulness of the paper in influencing their 

decision. 

4. PROS OF CRITICAL APPRAISAL IN PRACTICE 

• Critical appraisal allows us to: 

o Reduce information overload by eliminating irrelevant or weak 

studies 5 

o Identify the most relevant papers 

o Distinguish evidence from opinion, assumptions, misreporting, 

and belief 

o Assess the validity of the study 

o Assess the usefulness and clinical applicability of the study 

o Ensures a thorough assessment of the research 6 

o Recognises the strengths and weaknesses of the research 

o Develops a better understanding of the research methods used 

o Provides the ability to relate the published research to your 

situation 

o Ensures any bias in the research is identified 






3 

II. Concepts & Definitions 

ALLOCATION CONCEALMENT 

• Allocation concealment ensures that a randomised trial will genuinely 

remove any influence over the allocation process. 

• Allocation concealment is a different concept to blinding. It means 

that the person randomising the patient does not know what the next 

treatment allocation will be. 

• It is important as it prevents selection bias affecting which patients 

are given which treatment (the bias randomisation is designed to 

avoid) 7 . 

• The best way of ensuring allocation concealment is to use a 

centralised service, since this cannot be subverted by investigators 

and provides independent verification that it was not possible for the 

investigators to know the allocation sequence in advance 

ACCURACY 

• Accuracy refers to how close a measurement is to the true or 

accepted value. It indicates how often a test is truly positive 

or negative, as a proportion of all tests. 

Accuracy=----------------- 

BLINDING 

A+D 

A+B+C+D 

Case 

positive 

Case 

negative 

Test positive 

a b 

Test 

negative 

• Blinding is a procedure in which one or more parties in a trial are kept 

unaware of which treatment arms participants have been assigned 

to, in other words, which treatment was received. 

• It is an important aspect of any trial done in order to avoid and 

prevent conscious or unconscious bias in the design and execution of 

a clinical trial. 

• Blinding aims to reduce other forms of bias, by ensuring knowledge 

of the trial intervention does not influence other aspects of the 

patient’s treatment or assessment. 

c 

d 



LEVELS OF BLINDING 

1. None / unblinded 

• Blinding is not possible or practical for many trials such as those 

testing medical devices or involving surgery. Trials of complex 

interventions such as health care policies or staff training methods 

are also not easily blinded. 

• Where blinding isn't possible it is important to have an objective 

outcome measure that can't be easily influenced by the observer. 

• Alternatively, it may be possible to use observers not involved in the 

patients' care who assess patient outcome without knowing the 

treatment group (blinded outcome assessment) 8 . 

2. Single blind 

• This usually refers to the patient being blinded to the treatment given 

but not the administering clinician. Trials of medical devices or policy 

in intensive care are usually of this nature because the patient is not 

fully conscious. Sometimes surgical trials can be single blinded if two 

different types of surgery are being compared or even if surgery is 

compared to no surgery (by making a placebo incision in the control 

group for instance). 

3. Double blind 

• Neither the patient nor clinician know which treatment the patient is 

randomised to. Placebo controlled drug trials are usually double 

blind. It may sometimes be possible for the clinician to guess which 

treatment the patient has received by blood markers or other side 

effects. 

• If this is the case the simple randomisation code (see below) is not 

recommended because the clinician may break the blind on all 

patients by deducing the simple coding system from one patient. 

CHANCE, BIAS AND CONFOUNDING 

• Chance = Random error, which leads to imprecision 

• Bias = Systematic error, which leads to inaccuracy 

• Confounding = Error of interpretation, which leads to false 

conclusion 

• There are three reasons why the findings of a research study may not 

be valid: 






5 

1. The results may have been affected by chance (i.e. due to a 

random error) 

2. The results may have been affected by bias (i.e. a systematic 

error). 

3. The results may have been misinterpreted, and ascribed to one 

factor, when another factor (a confounder) was actually 

responsible. 

A. CHANCE 

• Chance is a random error appearing to cause an association between 

an exposure and an outcome. The probability of a random error is 

estimated using statistics (p values and confidence intervals). 

• The impact of random error depends upon how much variation there 

is in the population studied and the number of observations used to 

estimate the measurement (the sample size). 

• Random error will determine the precision of the results. 

• The greater the sample size, the less the overall estimate will be 

affected by random error, and the more precise the estimate will be. 

B. CONFOUNDING 

• Confounding is an error of interpretation, which leads to false 

conclusion. It describes the situation where the apparent association 

between a factor and an outcome is actually mediated by another 

unmeasured factor (the confounder). The results of the study may be 

precise and accurate, but they are misinterpreted and a false 

conclusion is drawn. 

• A confounding variable is a variable that, if removed, results in a 

change in the outcome variable by a clinically significant 

amount." It is a type of bias which will result in a distortion of the 

measured effect. If a confounder is known, it can be taken into 

account during analysis. Confounding may happen when we look for 

an association between a factor and an outcome (for example, 

between drinking coke and developing Colon cancer). 

• A confounding factor must be 9 : 

o Associated with the exposure but not a consequence of it: 

• A confounding factor cannot be on the causal pathway 

between exposure and disease 

• It must be present unevenly between groups to cause 

distortion of the measured effect 



REGRESSION 

• A statistical technique where all known confounders are 

held constant so that an association between variables can 

be examined. 

RISK REDUCTION 

1. EVENT RATE 

• The event rate is the proportion of people in the population who 

experience the particular event. The event rate changes according to 

baseline risk. While an event rate is reported in a clinical trial, you can 

only ever estimate an event rate for your patient using an 

understanding of their disease and risk factors 10 . 

2. RELATIVE RISK REDUCTION 

• The relative risk reduction is the difference in event rates between 

two groups, expressed as a proportion of the event rate in the 

untreated group. 

RRR 

CER - EER 

= ---------------- 

-- CER 

Example 1: 

• If 20% of patients die with treatment A, and 15% die with treatment 

B, the relative risk reduction is 25%. If the treatment works equally 

well for those with a 40% risk of dying and those with a 10% risk of 

dying, the absolute risk reduction remains 25% across all groups. 

Example 2: 

• The relative risk of developing lung cancer (event) in smokers 

(exposed group) versus non-smokers (non-exposed group) would be 

the probability of developing lung cancer for smokers divided by the 

probability of developing lung cancer for non-smokers. 

• The relative risk does not provide any information about the absolute 

risk of the event occurring, but rather the higher or lower likelihood 

of the event in the exposure versus the non-exposure group 11 . 

3. ABSOLUTE RISK REDUCTION 

• The absolute risk reduction is the arithmetic difference between the 

event rates in the two groups. It is the difference in rates of bad 

outcomes between experimental and control group in a trial. 

• This varies depending on the underlying event rate, becoming smaller 

when the event rate is low, and larger when the event rate is high. 






7 

1 

NNT = ------------- 

-- ARR 

RELIABILITY 

ARR= |CER-EER| = C/(C+D) - A/(A+B) 

• In the example above, there is a 5% absolute risk reduction with 

treatment B if the event rate is 20%. However, as the event rate 

increases to 40%, the absolute risk reduction increases to 10%. 

• As the event rate decreases to 10%, the absolute risk reduction 

decreases to 2.5%. The treatment still works just as well, but the 

numbers have changed. If a patient is told that treatment B reduces 

their risk of dying by 25% (the relative risk reduction), they may make 

a different decision to the one they would make when told that 

treatment B reduces their risk of dying by 2.5%. 

4. NUMBER NEEDED TO TREAT 

• The number needed to treat is calculated as 1/ARR. 

• It is the number of people that you would have to treat with 

treatment B in order to save one additional life. 

• In the examples above, treatment B may give a NNT that varies from 

10 to 40 depending on the expected event rate. 

• NNTs are always rounded up to the nearest whole number. 

❖ The higher the NNT, the less effective is the treatment. 

❖ The lower the NNT, the better. 

❖ The Higher the NNH, the better. 

• How repeatable a study is. In other words, the extent to which a 

research instrument consistently has the same results if it is used in 

the same situation on repeated occasions. 

• Validity is defined as the extent to which a concept is accurately 

measured in a quantitative study. For example, a survey designed to 

explore depression but which actually measures anxiety would not be 

considered valid. 

• Reliability is about the consistency of a measure, and validity is about 

the accuracy of a measure. 

SENSITIVITY (TRUE POSITIVES) 

• Sensitivity is the probability of a positive test amongst 

patients with the disease. It is the ability of a test to correctly 

classify an individual as ′diseased′. 



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9 

III. Evidence Hierarchy 

OVERVIEW 

• EBP hierarchies rank study types based on the rigour (strength and 

precision) of their research methods. 

• Different hierarchies exist for different question types, and even 

experts may disagree on the exact rank of information in the 

evidence hierarchies. 

• Most experts agree that the higher up the hierarchy the study design 

is positioned, the more rigorous the methodology and hence the 

more likely it is that the study design can minimise the effect of bias 

on the results of the study. 

• In most evidence hierarchies current, well designed systematic 

reviews and meta-analyses are at the top of the pyramid, and expert 

opinion and anecdotal experience are at the bottom 12 . 

Systematic Reviews 

and Meta-Analysis 

Randomised controlled 

trials 

Cohort studies 

Case-control studies 

Cross-sectional studies 

Ecological studies 

Case series and case reports 

Ideas, Editorials and Opinions 

Figure 1.3.1. Evidence Hierarchy 



7. META-ANALYSIS 

1. TRIALS, SYSTEMATIC REVIEWS AND META-ANALYSIS 

• Meta-analyses are now a hallmark of evidence-based medicine. 

• Meta-analysis is the statistical procedure for combining data from 

multiple studies. 

• When the treatment effect (or effect size) is consistent from one 

study to the next, meta-analysis can be used to identify this common 

effect. When the effect varies from one study to the next, metaanalysis 

may be used to identify the reason for the variation 13 . 

• In many medical specialties it is common to find that several trials 

have attempted to answer similar questions about clinical 

effectiveness; for example: Does the new treatment confer 

significant benefits compared with the conventional treatment? 

• Often many of the individual trials will fail to show a statistically 

significant difference between the two treatments. However, when 

the results from the individual studies are combined using 

appropriate techniques (meta-analysis), significant benefits of 

treatment may be shown. 

2. SYSTEMATIC REVIEWS 

• Systematic review methodology is at the heart of meta-analysis. 

• This stresses the need to take great care to find all the relevant 

studies (published and unpublished), and to assess the 

methodological quality of the design and execution of each study. 

• The objective of systematic reviews is to present a balanced and 

impartial summary of the existing research, enabling decisions on 

effectiveness to be based on all relevant studies of adequate quality. 

• Frequently, such systematic reviews provide a quantitative 

(statistical) estimate of net benefit aggregated over all the included 

studies. Such an approach is termed a meta-analysis. 

3. BENEFITS OF META-ANALYSES 

• Meta-analyses: 

o Overcome bias 

o Combine the results from many trials, therefore, have more 

power to detect small but clinically significant effects. 

o Give more precise estimates of the size of any effects uncovered. 






11 

o A good sensitivity analysis will explore, among other things, the effect 

of excluding various categories of studies; for example, unpublished 

studies or those of poor quality. 

o It may also examine how consistent the results are across various 

subgroups (perhaps defined by patient group, type of intervention or 

setting). 

o In meta-analyses without sensitivity analyses, the reader has to make 

guesses about the likely impact of these important factors on the key 

findings. 

6. PRESENTING THE FINDINGS 

a. Forest plot 

o The usual way of displaying data from a meta-analysis is by a 

pictorial representation (Forest plot). 

o This displays the findings from each individual study as a blob or 

square, with squares towards the left side indicating the new 

treatment to be better, whereas those on the right indicate the 

new treatment to be less effective. 

HOW TO READ A FOREST PLOT? 

Figure 1.3.9. Forest Plot by blogs.sas.com 

1) The vertical line 

o The vertical line is known as the “line of null effect.” 

o Relative statistics like OR or RR have a null effect value of 1. 

o Absolute statistics like Absolute Risk or ARR, the null difference value 

is 0 











experience. 








2. CRITICAL APPRAISAL APPROACH 

13 

2. CRITICAL 

APPRAISAL APPROACH 

I. How to Write a Good 

Abstract for a Scientific 

Paper 

1. Overview 

• The abstract of a paper is the only part of the paper that is published 

in conference proceedings. 

• The abstract is the only part of the paper that a potential referee sees 

when he is invited by an editor to review a manuscript. 

• The abstract is the only part of the paper that readers see when they 

search through electronic databases such as PubMed. 

• The abstract is the first question of the FRCEM critical Appraisal exam 

where a candidate is requested to provide a summary of the paper in 

less than 200 words. 



• Finally, most readers will acknowledge, with a chuckle, that when 

they leaf through the hard copy of a journal, they look at only the III. 

What is Therapeutic study? 

INTRODUCTION 

• In therapeutic research the basic ethical problem on the one hand is 

to expose the participating subject to a potentially ineffective 

intervention or to unknown risks. However, without such research on 

the other hand, the risk is to expose people to the uncontrolled risks 

of an intervention with a drug, the effectiveness and safety of which 

are not really known 14 . 

• Evaluation of a therapy involves comparing a group of patients 

receiving the therapy to a group of patients who do not receive it 

(the control group). 

• With a few rare exceptions (such as diseases that currently have 

100% mortality) a control group is always required to demonstrate 

that any improvement observed after treatment is not simply due to 

the natural course of the illness. 

• There are a number of key elements of the design of these studies 

that will determine whether the findings are valid and generalisable. 

1. SELECTION AND ALLOCATION OF STUDY 

PARTICIPANTS 

• Patients are selected to a trial by a process of recruitment that 

usually involves identification, assessment of eligibility, and then 

request for consent to participate. 

• Selection processes can occur at any of these stages to influence the 

constitution of the study population. 

• Selection of patients for a trial will affect generalisability. 

• If most eligible patients are identified and recruited then the results 

will be generalisable to the wider population. 

• If recruitment is highly selective then findings may not be 

generalisable. 

• Once patients have been selected into a trial, they are then allocated 

to a treatment or to control. 






15 

IV. Appraising Therapeutic 

Studies 

SECTION A. DOES THIS STUDY ADDRESS A CLEAR 

QUESTION? 

1. Were the following clearly stated? 

o Patients 

o Intervention 

o Comparison Intervention 

o Outcome(s) 

• Answers: Yes, can’t tell, No 

SECTION B. ARE THE RESULTS OF THIS SINGLE TRIAL 

VALID? 

A. The main questions to answer: 

2. Was the assignment of patients to treatments randomised? 

3. Was the randomisation list concealed? Can you tell? 

4. Were all subjects who entered the trial accounted for at its 

conclusion? 

5. Were they analysed in the groups to which they were randomised, 

i.e. intention-to-treat analysis 

B. Some finer points to address: 

6. Were subjects and clinicians ‘blind’ to which treatment was being 

received, i.e. could they tell? 

7. Aside from the experimental treatment, were the groups treated 

equally? 

8. Were the groups similar at the start of the trial? 

SECTION C. WHAT WERE THE RESULTS? 

Outcome total Yes No Total 

Experimental group a b a+b 

Control group c d c+d 



V. What is Diagnostic Test 

study? 

• KEY LEARNING POINTS: 

o When appraising a diagnostic test, ask yourself, "Are the patients 

in the study like mine? “[Grade of recommendation: A] 

o Bias is a systematic difference in the way patients in a study are 

handled [Grade of recommendation: A] 

o Post-test probability of a negative test is the same as negative 

predictive value [Grade of recommendation: A] 

o Post-test probability of a positive test is the same as positive 

predictive value [Grade of recommendation: A] 

1. TERMS USED IN REPORTING DIAGNOSTIC TEST 

DATA 

• The following terms are often used to report diagnostic test data. 

• It is well worth being absolutely sure that you know exactly what 

they mean. 

• Specificity, in particular, is often confused with positive predictive 

value. 

Gold standard 

• It is the criterion by which it is decided that the patient has, or does 

not have, the disease. 

Case positive 

• An individual with the disease in question, i.e. the gold standard is 

positive. 

Case negative 

• An individual without the disease in question, i.e. the gold standard is 

negative. 

Test positive 

• An individual with a positive result for the diagnostic test under 

investigation. 






17 

VI. Appraising Diagnostic 

Test Studies 

REMEMBER: 

1. The same reference standard should be applied to all patients, 

regardless of the results of the diagnostic test under evaluation. 

2. Work-up bias occurs when different reference standards are used 

depending on the perceived risk of a positive test. 

3. Incorporation bias occurs when the diagnostic test under evaluation 

forms part of the reference standard, e.g. cardiac markers in 

myocardial infarction. 

4. Those measuring the reference standard must be blinded to the test 

under evaluation, and vice-versa. 

5. Study populations should be representative of the population who 

would receive the test in routine practice. If the population is highly 

selected then this will bias estimates of sensitivity and specificity. 

6. Evaluations of diagnostic tests should include some assessment of 

reliability. The most common method for estimating reliability is to 

measure the Kappa score. 

• There are many checklists available for the assessment and critical 

appraisal of diagnostic test studies, as reporting is frequently 

inadequate. However, they all include some variation of the three 

main questions we need to ask; these are 15 : 



VII. Appraising a 

Systematic Review 

• Reviews collect together primary research and summarise their 

results and conclusions. 

• Systematic reviews are particularly useful because they usually 

contain an explicit statement of objectives, materials and methods, 

and should have been conducted according to explicit and 

reproducible methodology. 

• But, as with RCTs, systematic reviews should be critically appraised 

by users so they can decide for themselves whether their methods 

are valid, assess what the results are saying and decide whether 

these results can be applied locally. 

• Not all systematic reviews are rigorous and unbiased. 

• The reader will want to interrogate any review that purports to be 

systematic to assess its limitations. 

• The following questions provide a framework: 

o Is the topic well defined? 

• In terms of the intervention under scrutiny, the patients 

receiving the intervention (plus the settings in which it was 

received) and the outcome that was assessed? 

o Was the search for papers thorough? 

• Was the search strategy described? 

• Was manual searching used as well as electronic databases? 

• Were non-English sources searched? 

• Was the “grey literature” covered - for example, nonrefereed 

journals, conference proceedings or unpublished 

company reports? 

• What conclusions were drawn about the possible impact of 

publication bias? 

• Were the criteria for inclusion of studies clearly described and fairly 

applied? For example, were blinded or independent reviewers used? 

• Was study quality assessed by blinded or independent reviewers? 

Were the findings related to study quality? 






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VIII. Appraising Cohort 

Studies 

• Cohort studies are used to find out what has happened to patients. 

• A group of individuals is identified and watched to see what happens 

to them. 

• May have a control/comparison group, but not necessarily. 

• Essential features 

o The defining characteristic is the element of time. 

o A set of individuals is identified at one point in time and followed 

up at a later time to see what has happened to them. 

o The direction of time is always forwards – i.e. if in a study 

individuals are selected at one point and traced backwards to see 

how they were at some point in the past, it is not a cohort study. 

• Complications 

o Some studies identify a set of patients at some point in the past 

and follow them up to the present – this is a cohort study 

because time flows forward from the point at which the patients 

are identified. 






21 

IX. Appraising Case Control 

Studies 

11 QUESTIONS TO HELP YOU MAKE SENSE OF CASE 

CONTROL STUDY 16 

• Three broad issues need to be considered when appraising a case 

control study: 

o Are the results of the trial valid? (Section A) 

o What are the results? (Section B) 

o Will the results help locally? (Section C) 

• The first two questions are screening questions and can be answered 

quickly. If the answer to both is “yes”, it is worth proceeding with the 

remaining questions. 

SECTION A. ARE THE RESULTS OF THE STUDY VALID? 

Screening Questions 

1. Did the study address a clearly focused issue? 

• Tip: A question can be focused in terms of: 

o The population studied 

o The risk factors studied 

o Whether the study tried to detect a beneficial or harmful effect? 

2. Did the authors use an appropriate method to answer their 

question? 



X. Appraising Qualitative 

Research 

10 QUESTIONS TO HELP YOU MAKE SENSE OF 

QUALITATIVE RESEARCH 17 

• Three broad issues need to be considered when appraising a 

qualitative study: 

o Are the results of the study valid? (Section A) 






Screening Questions 

1. Was there a clear statement of the aims of the research? 

• Tip: Consider: 

o What was the goal of the research? 

o Why it was thought important? 

o Its relevance 

2. Is a qualitative methodology appropriate? 


o If the research seeks to interpret or illuminate the actions and/or 

subjective experiences of research participants 

o Is qualitative research the right methodology for addressing the 

research goal? 

Is it worth continuing? 

Detailed questions 

3. Was the research design appropriate to address the aims of the 

research? 


o If the researcher has justified the research design (E.g. have they 

discussed how they decided which method to use)? 






23 

XI. Appraising Economic 

Evaluations 

12 QUESTIONS TO HELP YOU MAKE SENSE OF 

ECONOMIC EVALUATIONS 18 

• Three broad issues need to be considered when appraising an 

economic evaluation study: 

o Are the results of the study valid? (Section A) 








3. COMMONLY ASKED 

QUESTIONS 

QUESTIONS 1 

1. What is the purpose of randomization 

• The main purpose of randomisation is to avoid bias by distributing the 

characteristics of patients that may influence outcome randomly 

between treatment groups so that any difference in outcome can be 

explained only by treatment. 

• Ensures that each patient has an equal chance of receiving any of the 

treatments under study, 

2. What does double blind mean 

• Double blind means that neither the patients nor the investigators 

know what intervention (active treatment or placebo) the patient has 

received. 

3. What is a convenience sample 

• A convenience sample is one that is selected because it is close at 

hand, available, attending when the investigators are present etc. 

4. Give one advantage of a convenience sample 

• The principal advantage is feasibility (i.e. convenience). It allows the 

researcher to obtain basic data and trends regarding his study 

without the complications of using a randomized sample. 

• Very useful for detecting relationships among different phenomena. 

5. Give one disadvantage of a convenience sample 

• The most obvious criticism about convenience sampling is sampling 

bias and that the sample is not representative of the entire 

population. 

• Therefore, results of the study cannot speak for the entire population 

(Not generalisable). 

• This results to a low external validity of the study. 

6. What is continuous data 

• Continuous data is numerical data that, in theory, can take any value 

e.g. blood pressure, Heart rate, weight, age... 





3. COMMONLY ASKED QUESTIONS 

25 

QUESTION 3 

Hoffmann et al. Coronary Computed Tomography for Early Triage of Patients with 

Acute Chest Pain. Journal of the American College of Cardiology 2009;53:1642- 

1650. 19 

1. Provide a no more than 200-word summary of this paper. Only the 

first 200 words will be considered – short bullet points are acceptable. 

Maximum of 8 points available. 

Answer 

• Diagnostic observational cohort study (1 point – ½ mark if only 

observational or only diagnostic. No marks if cohort only) 

• Study population – Patients presenting to the ED with chest pain 

with non-ischaemic initial ECG and normal initial troponin (1 point– 

must get all three elements to get mark) 

• Both clinicians and investigators were blinded (1 point) 

• Test of interest – Coronary computed tomography angiography (1 

point) 

• Reference (gold) standard – Diagnosis of ACS according to American 

Heart Association/American College of Cardiology/European Society 

Guidelines (after hospitalisation) (1 point) 

• Results 

• For plaque on CTA (presence of coronary artery disease): 

o Sensitivity 100% (95% CI 98-100%) 

o Negative predictive value 100% (85% CI 89-100%) 

o Specificity 54% (95% CI 49-60%) 

(1 point – must get all three for mark, ½ mark if 2 out of three) 

• For stenosis on CTA (> 50% luminal narrowing): 

o Sensitivity 77% (95% CI 59-90%) 

o Negative predictive value 98% (85% CI 95-99%) 

o Specificity 87% (95% CI 83-90%) 

(1 point – must get all three for mark, ½ mark if 2 out of three) 

• Likelihood ratio also accepted 

• Conclusion – the authors conclude that because half of low to 

intermediate risk chest pain patients were free of CAD and had no 

ACS, early coronary CTA may significantly improve patient 

management in the ED. (1 point) 

• Coronary CTA diagnosed CAD independent of TIMI score or troponin 

etc’ not accepted. 



INDEX 

A 

Absolute risk, 27, 83, 84, 121 

Absolute risk reduction, 27, 84, 121 

Accuracy, 3 

Allocation concealment, 3, 116 

Ascertainment bias, 6 

Attention bias, 7 

B 

Bayes theorem’, 127 

Bias, 4, 6, 38, 77, 115, 125, 167, 189 

Blinding, 3, 4, 40, 117, 133 

Blob, 52, 53 

Block-randomisation, 117 

C 

Case control studies, 36 

Case fatality rate, 128 

Case negative, 125 

Case positive, 125 

Case series, 35 

Case-control studies, 57 

Centripetal bias, 11 

Chance, 4, 5, 19 

Chi-squared test, 95 

Clinical prediction rule, 12 

Clinical review bias, 7 

Clinical trials, 58 

Cochrane’s q statistic, 17, 47, 55 

Coefficient of variation, 92 

Cohort studies, 37, 57 

Comparator review bias, 7 

Composite endpoint, 15, 97 

Confidence intervals, 76, 77 

Confounding, 4, 5, 189 

Confounding bias, 7 

Consort statement, 12, 104 

Convenience sampling, 13, 73 

Correlation coefficient, 93 

Cox proportional-hazard model, 13 

Critical appraisal, - 1 -, 1, 2, 99, 149 

Cross sectional study, 35 

Crossover studies, 58 

D 

Derivation procedures, 30 

Diagnostic access bias, 7 

Diamond, 53 

E 

Effectiveness, 1, 12, 14, 25, 39, 43, 44, 

49, 76, 102, 107, 115 

Efficacy, 14 

Egger’s regression test, 45 

Endpoints, 14 

Event rate, 27, 82, 83 

Evidence based medicine, 1 

Expectation bias, 8 

Explanatory research, 24, 25 

F 

Factorial design, 15 

False negatives, 126 

False positives, 126 

Fishers exact test, 95 

Fixed-effects models, 13 

Follow up bias, 8 

Forest plot, 16, 47, 52, 54 

Funnel plot, 44, 45 

G 

Gaussian distribution, 88 





INDEX 

27 

Generalisability, 30, 105 

Gold standard, 125, 178 

Gold standard, 8, 131 

Grade of recommendation, 16 

H 

Hawthorne effect, 7 

Hazard rate, 19 

Hazard ratio, 19 

Heterogeneity, 16, 46, 47, 54, 189 

Heterogeneity, 16, 46 

Hypothesis, 17, 75 

I 

I² statistic, 17, 47, 55 

Incidence rate, 127 

Inclusion bias, 8 

Incorporation bias, 9 

Index test review bias, 9 

Intention to treat analysis, 17, 120 

Intention-to-treat analysis, 60 

Interobserver variability, 17 

Interquartile range, 91, 167 

Intraobserver variability, 18 

Investigator bias, 9 

J 

Jadad, 18 

K 

Kaplan-meier curve, 19 

Kappa, 19, 20, 85 

Kruskal-wallis test, 94 

Kruskal-wallis test, 96 

L 

Last observation carried forward 

analysis, 62 

Likelihood ratio of negative test, 21, 

130 

Likelihood ratio of positive test, 21, 131 

Likelihood ratios, 20, 130 

M 

Mann whitney u test, 94 

Mann-whitney test, 94 

Mean, 90, 92 

Measurement bias, 9 

Measures of central tendency, 90 

Median, 90 

Meta-analysis, 49, 50 

Metaregression, 22 

Minimisation, 67 

Mixed-effects models, 14 

Mode, 91 

Mortality rate, 128 

Multivariate analysis, 22 

N 

Negative predictive value, 126, 127 

Neyman bias, 10 

N-of-1 trials, 59 

Non-inferiority studies, 60 

Non-parametric methods, 93 

Number needed to treat, 28, 84, 122 

O 

Observer bias, 10 

Odd ratio, 22 

Odds ratio, 83 

Outcomes, 14, 15, 97 

P 

Parametric statistical test, 93 

Patient spectrum, 133 

Per-protocol analysis, 17 

Per-protocol analysis, 61 

Popularity bias, 10 



Positive predictive value, 127 

Post-test odds, 23 

Post-test probability, 23 

Power, 23, 82 

Pragmatic research, 24 

Precision, 25 

Pre-test odds, 23 

Pre-test probability, 23 

Prevalence, 10, 126, 127, 128, 129, 168 

Primary outcome, 15, 97 

Publication bias, 10, 44, 45 

P-value, 75 

Q 

Quadas tool, 134 

Quantitative studies, 57 

R 

Random-effects models, 14 

Randomisation, 26, 63, 64, 65, 66, 116 

Randomised controlled studies, 39, 58 

Range, 91 

Recall bias, 11 

Receiver operator curve, 26 

Referral bias, 11 

Regression, 27, 55 

Relative risk, 27, 83, 84, 121 

Relative risk reduction, 27, 84, 121 

Reliability, 28, 133 

Reporter bias, 11 

Roc curve, 144 

S 

Sample size, 70 

Sampling bias, 11 

Selection bias, 11 

Sensitivity, 28, 29, 51, 126, 128, 129, 

142, 169, 172, 177, 181 

Sensitivity, 28, 29 

Skewed distribution, 89 

Snout, 126 

Specificity, 29, 125, 126, 127, 128, 129, 

142, 169, 172, 177 

Specificity, 29 

Sppin, 127, 129 

Spread of data, 93 

Standard deviation, 92 

Standard error of the mean, 92 

Stard, 134, 135 

Surrogate endpoint, 15, 97 

Survival analysis, 29 

Systematic review, 29, 41, 42, 147 

T 

Telephone randomisation hotline, 117 

Test negative, 126 

Test positive, 125 

Therapeutic personality bias, 12 

True negatives, 126 

True positives, 126 

T-test, 95 

Type 1error, 30 

Type 2 error, 30 

Type i error, 80 

Type ii error, 81 

V 

Validation procedures, 30 

Validity, 28, 30 

Variance, 92, 95 

Verification bias, 12 

Volunteer bias, 12 

W 

Wilcoxon rank-sum test, 96 

Withdrawal bias, 12 

Work up bias, 12 





INDEX 

29 









experience. 






References 

1 

Sackett DL, Strauss SE, Richardson WS, Rosenberg W, Haynes RB. Evidence-based Medicine. How to practice 

and teach EBM. London: Harcourt,2000. 

2 

Akobeng A. Principles of Evidence-based Medicine. Arch Dis Child2005; 90: 837-40 

3 

Jadad A. Randomised Controlled Trials. London: British Medical Journal Books, 1998 

4 

Gethin G. Understanding Research. Wounds UK 2009; 5:86 

5 

Dissecting the literature: the importance of critical appraisal by Kirsty Morrison 

6 

https://latrobe.libguides.com/criticalappraisal/introduction 

7 

Blinding and allocation concealment by sealed envelope 

8 

Blinding and allocation concealment by sealed envelope 

9 

Bias and Confounding, Life in the fast lane 

10 

Understanding absolute and relative risk reduction by Faculty of Medicine, Dentistry and Health Sciences. 

UWA Medical and Dental 

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Andrade C. Understanding relative risk, odds ratio, and related terms: as simple as it can get. J Clin 

Psychiatry. 2015 Jul;76(7):e857-61. 

12 

Hoffman, T., Bennett, S., & Del Mar, C. (2013). Evidence-Based Practice: Across the Health Professions (2nd 

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13 

Comprehensive meta-analysis at https://www.meta-analysis.com/pages/why_do.php 

14 

Assessment and Application of Therapeutic Effectiveness, Ethical Implications of 

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15 

Diagnostic test studies: assessment and critical appraisal. BMJ Best Practice. Available at 

https://bestpractice.bmj.com/info/toolkit/learn-ebm/diagnostic-test-studies-assessment-and-critical-appraisal/ 

16 

Critical Appraisal Skills Programme (CASP) Case Control Study Checklist 13.03.17 Available at:: 

https://www.cinj.org/sites/cinj/files/documents/11QuestionstoHelpYouMakeSenseofaCaseControlStudy.pdf 

Accessed: 28/12/2019 

17 

Critical Appraisal Skills Programme (2018). CASP Qualitative Checklist. [online] Available at::: 

https://journals.plos.org/plosone/article/file?type=supplementary&id=info:doi/10.1371/journal.pone.0180127.s00 

2 Accessed: 28/12/2019 

18 

Critical Appraisal Skills Programme (2018). CASP Economic Evaluation Checklist. [online] Available at 

https://casp-uk.net/wp-content/uploads/2018/01/CASP-Economic-Evaluation-Checklist-2018.pdf Accessed: 

28/12/2019 

19 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2747766/pdf/nihms114746.pdf

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