Randomised control trials Flashcards

1
Q

What type of study is an RCT

A

Analytic intervention study

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

RCT design

A

A group of people are randomly assigned to a control or intervention arm, then followed up and compared

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Key features of an RCT

A

Randomisation- confounders should be equally shared between groups. Method of randomisation should explicitly stated
Allocation concealment- minimises selection bias (conceal allocation sequence from everyone- should state how it was)
Blinding- single (particpants)/ double (participants and researcher)/ triple (participants, researcher and statistician)
Intention to treat analysis- analysing according to allocation (regardless of adherence/ drop-out/ contamination)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Importance of outcome measure

A

Need to relevant to the participants
If it is proxy, need confidence it is suitable
Reliable (produces consistent, reproducible estimates of true effect)
Valid (measures what it says it does)
Responsive (can detect changes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Other aspects of RCTs

A

Equipoise (genuinely don’t know if intervention or control is better)
Ethics- cannot cause harm in either intervention or control
Choice of control (sham intervention/usual care/placebo)
Sample size (need sample size calculations- larger the sample, the greater the precision (CI))

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Problems with RCTs

A

Non-adherence
Performance bias (differences in how groups treated)
Contamination
Detection bias (if outcomes detected differently between groups)
Potentially attrition bias if certain groups dropped out/ lost to follow-up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is per-protocol analysis

A

A secondary, exploratory analysis. It estimates the effect of adhering to a treatment
May be done if there was high contamination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Interpretation of outcomes in RCTs

A

Mean difference
Relative risk
Odds ratio
Survival analysis
Need to consider if the results are applicable to your local population

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are cluster RCTs

A

An RCT where groups of people are randomly assigned to an arm, rather than individuals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why are cluster RCTs done

A

Done when there is a high risk of high contamination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Random methods of sampling

A

Simple random (random number generator)
Cluster sampling
Stratified sampling (when you want to compare relatively small sub-groups (selectively recruit higher proportion of small groups to increase statistical power and sample size) or when measurement is likely to vary between sub-groups)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Non-random methods of sampling

A

Systematic sampling (pick every nth person)
Convenience sampling (those most available- easiest but volunteer bias)
Snowball sampling (ask participants to recommend others who meet the pre-specified criteria)
Street survey (pick people who appear to meet the criteria on the street, often they ask a specified number of men/women/age groups- quota sampling)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly