Critical Appraisal

Question 1

Definition evidence based medicine

Answer 1

The conscientious, explicit and judicious use of current best evidence in making decisions about the care of the individual patient

Question 2

5 steps of evidence based Medicine

Answer 2

1. Question
   (formulate clinical qu)
2. Evidence
   (search for best evidence to answer qu)
3. Critically appraise evidence
   (Validity, impact and applicability)
4. Application
   (apply results to clinical practice, integrating critical appraisal with clinic expertise and patients views and circumstances)
5. Monitor
   (Monitor the process, evaluating the effectiveness and efficacy of the whole process, and identifying ways of improving both for the future)

Question 3

Definition critical appraisal

Answer 3

Assesses validity of the research and statistical techniques employed in studies, and generated clinically useful information from them.

It seems to answer the 2 major qus:

1. Does the research have internal validity?
2. Does the research have external validity?

Question 4

Internal validity definition

Answer 4

To what extent a study measures what it set out to measure.
How good are the research methods used by the researchers to answer the clinical qu
(Efficacy)

Question 5

External validity definition

Answer 5

To what extent can the results from the study be generalised to a wider population? Will the results be the same in real life settings?
(Effectiveness)

Question 6

Efficacy definition

Answer 6

The impact of interventions under optimal (trial) conditions

Internal validity

Question 7

Effectiveness definition

Answer 7

Describes whether the interventions have the intended or expected effect under ordinary (clinical) circumstances
(External validity / generalisability)

Question 8

Structure for formulating a clinical question

Answer 8

PICO

Patient / problem
Intervention
Comparison (not always needed)
Outcome

Question 9

What is a peer reviewed journal?

Answer 9

A publication that requires each submitted article to be independently examined by a panel of experts, who are non-editorial staff of the journal.
Majority of peers need to approve to be considered for publication.
Anonymous process (can be double blinded).

Question 10

Benefits of peer review

Answer 10

• Forces authors to meet certain standards laid down by researchers and experts in that field.
• More likely that mistakes or flaws detected

I.e quality assurance.

Therefore peer reviewed journals generally held in greater esteem

Question 11

Disadvantages of peer review process

Answer 11

• Delay between submission and publication
• Peer reviewers might guess identity of author(s)
• Revolutionary or unpopular conclusions can face opposition leading to preservation of the status quo.
• Still doesn’t guarantee lack of errors or fraudulent research

Question 12

The primary hypothesis

Answer 12

The clinical question is formalised into a position statement that will be proven true or false in the experiment. Generated before data collection.
Same or closely related to the clinical question.

NB
Not all studies designed to test hypothesis. Some studies (case reports or qualitative) can be used to generate hypotheses

Question 13

What is a confounder?

Answer 13

A confounder has a triangular relationship with both the exposure and the outcome, but most importantly, it is not on the causal pathway.
It makes it appear as if there is a direct relationship between exposure and the outcome or it might even mask an association that would otherwise have been present.

Can cause overestimation or underestimation of the true association and Can even change the direction of the observed effect.

Question 14

What is a positive confounder?

Answer 14

Results in an association between two variables that are not associated.

Question 15

What is a negative confounder?

Answer 15

Masks an association that is really present

Question 16

How would a good study deal with confounders?

Answer 16

• accept possibility that confounding May be an issue
• list confounding factors and explain their impact on any relationship under investigation
• describe how confounding factors were controlled at the design and analysis stage

Question 17

Dealing with confounders

Answer 17

Once identified there are a number of techniques that can be used to deal with confounding either at design stage or analysis stage:

• eliminate confounding factors altogether (exclusion criteria)
• nullify their effects by spreading them equally between the different groups of the study (randomisation)
• account for their effects on the results using statistical techniques (eg regression)

Question 18

Difference between bias and confounding

Answer 18

Bias leads to the wrong results

Confounding leads to the wrong conclusion

Confounding differs from bias in that confounding is not caused by a mistake made by the researchers, it arises from a real life relationship that already exists between exposures and outcomes under consideration

Question 19

Bias definition

Answer 19

• bias leads to the wrong results
• if a study suffers bias the results data are incorrect due to the bias

Ie the conclusion is correct judged solely on collected data but if there had been no bias different results would have been generated

Question 20

Confounding definition

Answer 20

Results data are correct but the interpretation of the results is wrong leading to the wrong conclusion. Happens when researchers don’t appreciate the entire situation.

Question 21

Types of bias

Answer 21

• selection bias
• performance bias
• detection bias
• attrition bias
• reporting bias

Question 22

Selection bias

Answer 22

Problem with recruiting and allocating subjects.

Deal with this by random allocation and concealment of allocation

Question 23

Performance bias

Answer 23

Problem with way data gathered in study, such results have been unduly influenced by the expectations of researchers and subjects.

To deal with this: blinding and placebo arms

Question 24

Detection bias

Answer 24

Can be minimised by blinding

Question 25

Attrition bias

Answer 25

It is important to see whether the intention to treat or the per protocol approach was used because this may present a biased result

Question 26

Reporting bias

Answer 26

Outcome reporting bias, publication bias

Question 27

In relation to bias a good study will

Answer 27

Strive to use method to minimise risk of bias

Acknowledge the presence of bias when it occurs and discuss how results may have been influenced

Suggest how future researchers should modify their methods to reduce risk of bias if possible

Question 28

With regards to population and sampling a good study will

Answer 28

• define target population
• describe sampling method
• list inclusion criteria and relate them to the aims of the study
• list and explain exclusion criteria
• illustrate how many people were included and excluded, often in the form of a flowchart or table
• explain how sample size determined
• comment on how the sample population represents the target population

Question 29

In relation to selection bias a good study will….

Answer 29

Allow sufficient time and resources to recruit subjects without resorting to
Shortcuts

Explain how selection process minimised selection bias

Acknowledge mistakes or methodological compromises that were made

Make suggestions on how mistakes can be avoided in future research if possible

Question 30

3 key concepts of critical appraisal

Answer 30

1. Validity
2. Trustworthiness of results
3. Value and relevance

Question 31

Validity of study

Answer 31

Rigour of study and extent to which the conclusions of research are true in context in which restate was undertaken (internal validity).

A more valid:

• Design
• Method
• Procedure

Produces less bias results giving us more reliable generalisable conclusions