AFP interview

Question 1

hierarchy of evidence

Answer 1

1) Meta-analysis/ Systematic Review
2) RCT
3) Cohort
4) Case control
5) Cross sectional
6) Case series (collection of similar cases)

Question 2

Meta analysis definiton

Answer 2

An overview of a topic in which the results of all of the included studies are similar enough statistically that the results are combined and analysed as if it were one study.

A meta-analysis uses the quantitative results from the individual studies, pools them together using a statistical method, and produces a new single quantitative result. This new quantitative result is known as the ‘pooled treatment result’and is depicted graphically in a forest plot

Question 3

Systematic review definition

Answer 3

An overview of primary research on a particular research question that tries to identify, select and appraises all relevant high quality evidence to answer the research question

Question 4

A disadvantage of meta-analysis & systematic reviews

Answer 4

Relies on published studies –> publication bias

Question 5

RCT definition

Answer 5

Cohort study

• People are randomly allocated to a treatment or control group

Question 6

5 advantages of RCTs

Answer 6

• Studies effect
• Has a control group (balances the confounders)
• Randomised
• Powered for analysis
• Blinding

Question 7

5 disadvantages of RCTs

Answer 7

• Expensive
• Time consuming
• Volunteer bias
• Not realistic clinical practice (e.g frequent
follow-ups)
• Can be ethically problematic

Question 8

Cohort study defintion

Answer 8

Longitudinal observational study - follows people with a common exposure (e.g smoking) over time to determine the risk of subsequent disease

Question 9

5 advantages of Cohort studies

Answer 9

• Studies risk factors (for common outcomes)
• Safe (ethics)
• Match characteristics
• Realistic patients
• Establish timing & directionality of events

Question 10

5 disadvantages of Cohort studies

Answer 10

• Cannot blind (difficult)
• Loss in follow-up (attrition bias)
• Expensive
• Hidden confounder
• Requires large sample sizes or long follow-up
for rare diseases

Question 11

Case control definition

Answer 11

Identifies two groups (with and w/o disease) and looks back for contributing factors

Question 12

4 advantages of case control studies

Answer 12

• Studies rare outcomes & disorders
• Small sample size required
• Quick & Cheap
• Safe (ethics)

Question 13

3 disadvantages of case control studies

Answer 13

• Recall bias (retrospective study)
• Selection bias
• Difficult to select control groups

Question 14

Cross-sectional study defintion

Answer 14

Descriptive study

• ‘Snapshot’ of a population at a given time in which disease and exposure status are measured at the same time

Question 15

2 advantages of cross-sectional studies

Answer 15

• Quick & Cheap

* Safe (ethics)

Question 16

4 disadvantages of cross-sectional studies

Answer 16

• Association not causation
• Recall bias
• Unequal group sizes
• Unequal distribution of confounders

Question 17

Case series definition

Answer 17

Collection of similar cases from a hospital or healthcare professional

Question 18

What is audit?

Answer 18

Review of (current) practice against a set standard

Question 19

What is research?

Answer 19

Study trying to find out what we should be doing with an aim to advance medical studies or protocols and procedures

Question 20

What is quality improvement?

Answer 20

A process by which we achieve better patient experience and outcomes

Question 21

What is research governance?

Answer 21

The range of regulations, principles and standards of good practice which ensure high quality research

Question 22

How is risk and risk ratio (same as relative risk) calculated?

Answer 22

AR = Absolute risk (No of events / no of people)

Risk ratio = (AR in treatment group/ AR in control group)

Question 23

What does a risk ratio of 1 (or CI including 1) mean?

Answer 23

No significant difference between intervention and control

Question 24

What does a risk ratio of 2 mean?

Answer 24

Events are two times MORE likely in the treatment group than the control group

Question 25

What does a risk ratio of 0.5 mean?

Answer 25

Events are 50% (0.5) LESS likely in the treatment group than the control group

Question 26

What is a type 1 error?

Answer 26

Rejection of null hypothesis when it was true (i.e. a false positive)

Think of a pregnant man (false positive)

Question 27

What is a type 2 error?

Answer 27

Failing to reject a false null hypothesis (false negative)

Think of someone who is pregnant but pregnancy test is negative < False negative (T2 error) is most dangerous because you are missing the disease

Question 28

Which criteria is used to report RCTs?

Answer 28

CONSORT

Question 29

Which criteria is used to report systematic reviews and meta analyses?

Answer 29

PRISMA

Question 30

Which criteria is used to report cohort studies and cross sectional studies?

Answer 30

STROBE

Question 31

What are the four steps to critiquing/presenting a paper or a graph?

Answer 31

1. PICO
2. internal validity (biases and confounders)
3. Results (statistical significance and clinical significance)
4. External validity (clinical relevance)

Question 32

What is selection bias and what are the two main ways it can arise?

Answer 32

A bias in assignment or selection of patients for a study that arises from study design rather than by chance, which occurs:
• when the subjects studied are not representative of the target population
• when the study and control groups are not matched properly, and so can affect the outcome of the study

Question 33

What is external validity?

Answer 33

Whether the results of the study can be applied to non-study patients or populations.

Question 34

What two methods can be used to reduce selection bias?

Answer 34

1. Randomised allocation

2. Restriction of inclusion criteria