A and P of an RCT - Jackson

Question 1

Define a RCT

Answer 1

A prospective study in which participants are allocated at random to receive

• Study treatment or control (i.e no study treatment) or
• one of two (or more) alternate treatments

Question 2

What does random allocation mean?

Answer 2

All participants have the same chance of being assigned to each of the study groups

Question 3

quasi- randomisation

Answer 3

Any method that allows foreknowledge of treatment that would be assigned e.g:
Alternate participants identified
Date invited to participate, alternate days/weeks/months
Participant surname, initials, DOB
Number on hosp records

There is a greater risk that the investigator will be aware which participant is in which group.

Question 4

methods of randomisation

Answer 4

Flip a coin 
Draw from a bag 
Random numbers table 
Computer generated sequences 
Stratified randomisation 
Block randomisation

Question 5

Stratified randomisation

Answer 5

Divide patients into key groups (e.g. sex) before randomisation
Ensures balance between groups for values of “key” variables
Important if study of small size, where chance imbalance more likely

Question 6

Block randomisation

Answer 6

Ensures numbers of participants in study groups kept even by creating “blocks” of sequences

Question 7

Blinding, why?

Answer 7

Useful when decisions about outcome are subjective (e.g. functional status, pain, cause of death)
Less useful when outcome of assessment is objective (weight, cholesterol, all cause mortality)

Question 8

Successful randomisation depends on what two inter-related processes

Answer 8

Generating a random number sequence to allocate patients e.g. flip a coin, use a random numbers table, or computer generated random numbers sequence
Concealing those involved (participants and investigators) from knowing which group a participant will be allocated to.

Question 9

Ethics and randomised trials?

Answer 9

Trials are only unethical where uncertainty exists about the research question

Question 10

RCTs and moderate effects and moderate biases

Answer 10

Required for detection of moderate treatment effects, particularly on outcomes which are relatively infrequent (e.g. death or hospitalisation)
Moderate treatment effects will not be reliably characterised in studies in which there are moderate biases

Question 11

The 3 phase types of RCTs

Answer 11

1) small dose ranging studies of toxicity, typically not randomised
2) small, short term studies of surrogate efficacy, sometimes randomised (to measure endpoint of a specific treatment)
3) large, long term studies of true efficacy and safety, always randomised

Question 12

Strengths and weaknesses of RCTs

Answer 12

strengths - only 1: addresses confounding
Weaknesses:
- too expensive
- Usually too small (lots of random error)
- Usually not ‘real world’
- Poor compliance