POPH192 - Lecture 21

Question 1

What type of study is randomised control trial?

Answer 1

analytic and interventional

Question 2

what does RCT measure?

Answer 2

similar to cohort, but instead of measuring exposure it randomises an intervention

Question 3

first step of a RCT?

Answer 3

1) identify source population

Question 4

second step of a RCT?

Answer 4

2) randomly select sample population who don’t have outcome of interest

Question 5

third step of a RCT?

Answer 5

3) randomise the sample to either the intervention or control groups

Question 6

fourth step of a RCT?

Answer 6

4) follow up overtime and see who develops the outcome

Question 7

fifth step of a RCT?

Answer 7

5) calculate measures of association and occurence

Question 8

What is randomisation?

Answer 8

• aka random allocation
• when participants are randomly allocated into either the control group or intervention group

(not the same as random selection!!)

Question 9

what is the purpose of randomisation?

Answer 9

• to control for confounding

(this is when another variable like age or sex distorts the relationship between exposure and outcome)

Question 10

what happens in successful randomisation?

Answer 10

• if done correctly, there should be the same proportion of known and unknown confounders in each group (meaning that groups are comparable)

Question 11

how can you tell randomisation has been successful?

Answer 11

by looking at the baseline characteristics (age, weight, sex etc) of both groups.

• if successful, they should be similar (don’t have to be identical)

Question 12

what are the 2 other variants of randomisation?

Answer 12

• cluster
• stratified (block)

Question 13

what is cluster randomisation?

Answer 13

subgroups are randomised instead of individuals

Question 14

what is stratified (block) randomisation?

Answer 14

participants are randomised within blocks

Question 15

what is the first way of protecting randomisation and it’s benefits?

Answer 15

concealment of allocation

Question 16

what is concealment of allocation?

Answer 16

the person randomising the participants doesn’t know what the next treatment allocation will be
- it is concealed and unpredictable

Question 17

how can you achieve concealment of allocation?

Answer 17

by a computer generated randomisation code

Question 18

what does concealment of allocation prevent?

Answer 18

selection bias
- from the other participants or their doctors from selecting the treatment they want

Question 19

what is the second way of protecting randomisation and it’s benefits?

Answer 19

intention to treat analysis

Question 20

what is the intention to treat analysis

Answer 20

this is when we analyse as we randomise
- it means you aren’t swapping people between groups and are maintaining the randomisation

Question 21

what effect does the intention to treat analysis give?

Answer 21

it gives a ‘real world’ effect
- people don’t take intervention perfectly in real life

Question 22

what is the other type of analysis for RCT?

Answer 22

‘per protocol’ analysis

Question 23

what is ‘per protcol’ analysis?

Answer 23

• when you analyse participants who fully completed the study protocol

Question 24

what does the per protocol analysis show/lose?

Answer 24

can show the efficacy of the treatment, but lose the benefits of randomisation

Question 25

what are the 3 types of bias that can occur in RCT?

Answer 25

• lack of blinding
• loss to follow up
• non-adherance

Question 26

what can lack of blinding do?

Answer 26

if people involved in the study know whether they were in the intervention or control group, it may influence them

Question 27

how can studies be blinded? what is the best way to describe this?

Answer 27

studies can be single blinded (participant) or double blinded (participant and researcher), but it is best to be specific on WHO is blinded in the study

Question 28

are all methods for blinding easy?

Answer 28

• certain methods can be used but sometimes it’s difficult
  e. g. if things like physiotherapy or surgery are the intervention

Question 29

what are the effects of loss to follow up?

Answer 29

if people leave the study, this can cause confounding and bias
- the ones who left could be different to the one’s who stayed

Question 30

what are the effects on non-adherance?

Answer 30

• participants are sometimes not good at following instructions
• if there is too much non-adherance, it can lead to bias

Question 31

what are the strengths of RCT?

Answer 31

• gold standard study design to test an intervention and cause and effect associations
• eliminate confounding and bias (if done well)
• calculate incidence, and measures of association

Question 32

what are the limitations of RCT?

Answer 32

• many exposures cannot be randomised
• need to have clinical equipoise
• expensive
• sometimes participants aren’t representative of general population, so are not generalisable
• not good for rare outcomes

Question 33

what is clinical equipoise?

Answer 33

genuine uncertainty about benefit/harm of the intervention