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MBBS Year 2 > Randomised Controlled Trials > Flashcards

Randomised Controlled Trials Flashcards

1
Q

Define a clinical trial

A

a clinical trial is an experiment in which a treatment is administered to humans in order to evaluate its efficacy and safety

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2
Q

What are the different types of a clinical trial?

A

uncontrolled trial - everyone gets the treatment
controlled trial - a treated group is compared with an untreated group (placebo) or a treated group is compared with a control group having ‘usual treatment’
randomised controlled trial - allocation to groups is determined by chance

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3
Q

What are the different types of controls?

A

geographical
historical
randomised

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4
Q

what are geographical controls?

A

patients with the same disorder seen at another hospital or clinic where the new intervention is not provided

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5
Q

what are historical controls?

A

patients with the same disorder seen in the past before the use of the new intervention

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6
Q

what bias occurs with the use of geographical or historical controls?

A

selection bias

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7
Q

what are the benefits of a randomised controlled trial?

A

helps ensure that the group receiving treatment A is similar to the group receiving treatment B
avoids selection/ allocation bias
only difference between the treatment and control group is the treatment

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8
Q

when are patients randomised in a RCT?

A

after they are deemed eligible and they have consented to participate

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9
Q

what is a single blind study?

A

the patient does not know what treatment they are receiving

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10
Q

what is a double blind study?

A

physicians and patients do not know what treatment the patient is receiving

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11
Q

what is the benefit of a double blind study?

A

it ensures that the use of other potential treatments, the assessment of the outcome and the decision to withdraw the patient is not influenced by clinician’s or patients knowledge of treatment

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12
Q

what are the different types of a randomised controlled trial?

A

parallel group
crossover
cluster randomised trials
factorial

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13
Q

what is the difference between a parallel group and a crossover?

A

in parallel group, each participant is randomly assigned to a group, and all the participants in the group receive (or do not receive) an intervention.
crossover involves patients swapping groups. so patients first receiving treatment switch over to the placebo group. each participant receives (or does not receive) an intervention in a random sequence

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14
Q

when is a parallel group study design used?

A

when effect of treatment is not reversible e.g cancer, heart attack

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15
Q

when is a crossover study it used?

A

when effect of treatment is reversible e.g. statins treating cholesterol

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16
Q

what are the advantages of cross over trials?

A

patient becomes their own control. able to see which period they felt better in (treatment v placebo)
smaller sample size to get same number of observations
better for subjective measurements

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17
Q

what are the disadvantages of cross over trials?

A

more time consuming

carry over effects - carry over effect of treatment into placebo period

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18
Q

why is a washout period required in a cross over trial?

A

it is a period when the patient does not receive anything to get rid off the effect of the previous treatment

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19
Q

what is a cluster randomised trial?

A

pre-existing groups of participants (e.g., villages, schools) are randomly selected to receive (or not receive) an intervention.

20
Q

what is the advantage of cluster randomised trials?

A

ability to study interventions that cannot be directed toward selected individuals and the ability to control for “contamination” across individuals, as all participants in the trial are affected by intervention even if only some receive it (e.g., one individual’s changing behaviors may influence another individual to do so)

21
Q

what is a factorial trial?

A

each participant is randomly assigned to a group that receives a particular combination of interventions or non-interventions (e.g., group 1 receives vitamin X and vitamin Y, group 2 receives vitamin X and placebo Y, group 3 receives placebo X and vitamin Y, and group 4 receives placebo X and placebo Y).

22
Q

what are the different phases in developing and evaluating a new drug?

A 
preclinical
phase 0
phase 1
phase 2
phase 3
phase 4
23
Q

what is the preclinical phase?

A

non human study

in vitro and in vivo animal studies to obtain preliminary efficacy, toxicity and pharmacokinetic information

24
Q

what happens in phase 0?

A

first in-human trials

small number of subjects given sub therapeutic doses to assess pharmacodynamics and pharmacokinetics

25
Q

what happens in phase 1?

A

screening for safety
testing of drug on healthy volunteers for dose ranging
determines whether the drug is safe to check for efficacy

26
Q

what happens in phase 2?

A

assess efficacy and safety
to determine whether drug can have a therapeutic effect
may be designed as case series or randomised controlled trial

27
Q

what happens in phase 3

A

assess efficacy and safety - important phase

RCT on large number of patients to determine what the therapeutic effect is

28
Q

what happens in phase 4?

A 
post marketing surveillance
safety surveillance (pharmacovigilance)
29
Q

why must all trials be registered prospectively?

A

journals will not consider trials for publication unless they are registered

30
Q

Give examples of the primary registries in the WHO network?

A

International Standard Randomised Controlled Trial Number (ISRCTN)
European Union Clinical Trials Register (EU-CTR)
Australian New Zealand Australia Clinical Trials Registry

31
Q

What are the advantages of registries?

A

assist in the planning of new trials
avoid unnecessary duplication of research
avoid subjecting patients to trials seeking evidence that is already available
encourage collaboration between research groups
facilitate optimal use of research funds by finding agencies

32
Q

how is relative risk calculated?

A

example:
calculate risk of death in treatment group and risk of death in control group
relative risk of death in treatment group compared to control group: risk of death in treatment group/ risk of death in control group

33
Q

what is intent treat analysis?

A

comparison of all subjects based on the treatment group assigned, regardless of whether they complied
it is the primary analysis. you can better reflect what happens in practice as some patients don’t take the treatment

34
Q

what is on treatment analysis?

A

comparison of subjects who actually took the treatment

35
Q

Why do you need to maximise compliance?

A

to ensure trial results are meaningful
preserves randomisation
poor compliance on intent to treat analysis reduces ability to detect treatment difference

36
Q

How do you maximise compliance?

A

selection of patients
double blind study design - so patients do not know what treatment they are receiving
run in period where all get treatment (to identify those who can’t tolerate it)

37
Q

how do you calculate the number needed to treat from the relative risk calculated in the study?
e.g trial of folic acid vs placebo for prevention of neural tube defects (in women with a previous NTD pregnancy)
risk of neural tube defect in folic acid group= 1%
risk of neural tube defect in placebo group= 3.5%

A

calculate absolute difference in risk
3.5% - 1% = 2.5%
calculate the inverse of the absolute different in risk
number needed to treat = 100/2.5 = 40
so 40 women (who had a previous NTD pregnancy) need to take folic acid to prevent 1 neural tube defect

38
Q

what is the number needed to treat?

A

average number of patients who need to be treated to prevent one additional bad outcome (i.e. the number of patients that need to be treated for one to benefit compared with a control in a clinical trial). It is defined as the inverse of the absolute risk reduction.

39
Q

what is the importance of sample sizes?

A

specify number of people to recruit prior to starting trial
number needed is calculated based on some prior information e.g expect relative risk of death of treatment A compared to B to be 2

40
Q

what is the problem of having a small sample size?

A

too few participants may not detect a real effect as study does not have enough statistical significance
larger sample sizes have greater statistical power

41
Q

what is statistical power?

A

The power of a statistical test is the probability that it correctly rejects the null hypothesis when the null hypothesis is false
statistical power is usually 85% or more

42
Q

what is meta analyses?

A

This is a mathematical technique that combines the results of individual studies to arrive at one overall measure of the effect of a treatment.
purpose to bring together all the evidence to more powerfully estimate the effect size
results of individual studies and a summary estimate often shown in a Forest plot

43
Q

what are the issues in meta analyses?

A

heterogeneity

publication bias

44
Q

what is heterogeneity?

A

variation in study results
caused by difference in study design, difference in participant characteristics, difference in intervention (e.g. drug dose), chance

45
Q

what methods can be used to avoid heterogeneity?

A

split up study into groups according to when the treatment was administered
order date when treatment was administered
order studies according to doses given

46
Q

what is publication bias?

A

studies with significant or favourable results more likely to be published
caused by: investigators, journal editors, journal peer reviewers
can be assessed statistically and graphically using a funnel plot

MBBS Year 2 (11 decks)

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