lecture 21

Question 1

what is a randomised control trial

Answer 1

participants randomly allocated into groups

there is a control/comparison group

testing effect of intervention / treatment

Question 2

how does a randomised control trial work

Answer 2

randomly assign exposure, then follow up to find out outcomes

Question 3

what is the difference between cohort and randomised control trials in terms of study type

Answer 3

cohort = observational

randomised control trial = intervention

Question 4

why randomise in a randomised control trial

Answer 4

random allocation in the study groups is the only way to ensure that all of the groups are as similar as possible

Question 5

what is confounding

Answer 5

something thats muddling up the effect that your seeing between the exposure and the outcome

Question 6

what is cluster randomisation

Answer 6

sometimes it is difficult to randomise individuals so you can randomise groups of participants instead

Question 7

what is the intention to treat analysis in a randomised control trial

Answer 7

• when participants are analysed as they were randomly allocated into their groups
• even if they did not stick to the group they were allocated

Question 8

what are the benefits to intention to treat analysis in a randomised control trial

Answer 8

• preserves the benefits of randomisation
• can more accurately reflect ‘real world’ effect of the intervention

Question 9

what is pre protocol analysis in a randomised control trial and when it is more appropriate

Answer 9

• analysed as treated ( what they actually did, not what group they were randomly assigned
• tends to be more appropriate for efficacy trials (does the medication work or not)

Question 10

what are the potential sources of bias in a randomised control trial

Answer 10

• lack of concealment of allocation
• lack of blinding
• loss to follow up
• non adherence

Question 11

why is concealment of allocation important in randomised control trials

Answer 11

it is important that the allocation sequence is concealed and unpredictable otherwise bias could be introduced by people picking the groups

Question 12

what are the strengths of a randomised control trial

Answer 12

• randomisation maximises the likelihood that potential confounders are evenly distributed between groups
• best way to test and intervention
• can calculate incidence (so can calculate relative risk and risk difference)
• temporal sequence is known
• strongest design for determining causation

Question 13

what are the limitations of a randomised control trial

Answer 13

• not all exposures are suitable to be randomly allocated
• can be difficult to achieve blinding
• potential for loss to follow up and non adherence
• resource intensive
• highly selective