Types of study

Question 1

Summarise the pyramid of evidence: top to bottom

Answer 1

Meta analysis 
Systematic Review 
RCT 
Cohort study 
Case control study 
Cross sec study 
Case report etc

Question 2

What is a meta analysis?

Answer 2

A statistical analysis of the results of several trials, which are combined to minimise bias, reach a more accurate true population effect, and increase statistical power of evidence. It is usually part of a systematic review

Question 3

What is a good thing to include in a meta analysis

Answer 3

A sensitivity analysis - it aims to determine the robustness of observed outcomes

Question 4

What is a sensitivity analysis

Answer 4

The repeat of the primary analysis or meta anaalysis, substituting alternative decisions for decisions that were arbitrary or unclear

Question 5

What is a systematic review

Answer 5

Meticulous, protocol driven lit review that critically analyses all published findings on a specfic research question

Question 6

What are advantages of a SR/MA

Answer 6

• easy to interpret
• time saving for clinicians
• reduces bias > conclusions are more reliable and accurate
• Results are more generalisable
• increased precision of results (as larger sample size > closer to TRUE pop mean and reduced T2E)

Question 7

What are disadvantages of a SR/MA

Answer 7

• selection bias at point of identifying studies
• may focus on studies in English only
• Over-geneeralisation
• can potentially replicate flaws of original studies
• may be dificultr to compare studies (if heterogeneous)

Question 8

What are advantages of a RCT

Answer 8

• Prospective, which allows to conclude causation
• Comparative, which allows to establish superiority
• Bias minimisation (randomisation, blinging, double blinding, allocation concealment, prospectrive design)
• minimises confounding factors (via randomisation)
• statistical reliablity

Question 9

What are DISADVANTAGES of RCT

Answer 9

• difficult and time consuming
• may be prone to underpowering (if sample size required is too big)
• long time period may result in loss of relevance
• applicability (as if testing for efficacy, may not be widely applicable)
• ethical (clinical equipoise and difficulty in obtaining informed consent )

Question 10

What is clinical equipoise

Answer 10

There needs to be GENUINE UNCERTAINTY in the medical community for which treatment is beneficial

Question 11

What is a cohort study?

Answer 11

Two or more groups of people are selected based on differences in their exposure to a particular agent and followed retrospectivellly or prospectively over a period of timw

Question 12

what type of cohort study ranks higher, prospective or retrospective?

Answer 12

PROSPECTIVE

Question 13

what are advantages of a cohort study?

Answer 13

• good for rare conditions
• direct estimation of disease incidennce rates, assesses temporal relationships, finds associations
• can assess multiple outcomes associated with multiple exposures

Question 14

What are advantages for prospective cohort study specificaally

Answer 14

can control design, sampling, data collection, follow up

Question 15

what are advantages of retrospetive cohort study only

Answer 15

time efficient, inexpensive, easy to obtain large samples

Question 16

what are disadvantages of prospective cohort study

Answer 16

expensive
can take a long time from exposure to outcome
cannot be used if disease has long latency period
loss to follow up, long follow up
confounding variables

Question 17

what are disadvantages of retrospective cohort study

Answer 17

less control ovr variables, susceptiblee to informartion and recall bias

Question 18

How does a case control study work

Answer 18

determines if exposure is associated with an outcome z
always RETROSPECTIVE

1. identify cases (group with outcome) and controls (group without outcome)
2. trace back to see which group had exposure

Question 19

Advantages of case control

Answer 19

• good for studying rare outcomes
• good for studying links where outcome occurs long time after exposure
• smaller sample size required (as no loss to follownup)
• quick, cheap, easy

Question 20

Disadvatages of case control

Answer 20

• retrospective - so makes it more difficult to establiish causal link
• difficult to match to control group
• recall bias / observer bias
• temporal relationship may be difficut
• not good for rare exposures

Question 21

what is a non-inferiority study

Answer 21

A trial with intent to demonstrate that the EXPERIMENTAL TX is not substantially different than the control

Question 22

How can you adjust for confounding factors?

Answer 22

By stratification, inclusion/exclusion criteria or matching

Question 23

What is the negative aspects of adjusting by stratification or inclusion / exclusion criteria?

Answer 23

Tighter inclusion/exclusion criteria make the study less externally valid