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MRCPsych Part B > Interventional Studies > Flashcards

Interventional Studies Flashcards

1
Q

What makes RCTs different from other studies?

A

Experimental intervention
Randomisation
Generalizability

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2
Q

In what ways are RCTs experimental?

A

One group is the control
The other receives an intervention

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3
Q

Types of randomisation

A

Simple
Block
Stratified
Minimisation
Quasi

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4
Q

Describe simple randomisation

A

Randomising each entrant separately e.g. using a computer generated list

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5
Q

What is block randomisation?

A

Randomisation occurs in a set of specified numbers e.g. blocks of 6 to ensure equal distribution between control and intervention group

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6
Q

Impact of larger block size in randomisation?

A

Lesser ability to predict allocation

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7
Q

What is stratified randomisation?

A

Baseline characteristics which may implicate final outcome are stratified so there is equal distribution between the groups.

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8
Q

Precision when using stratified randomisation?

A

Minimal if large study

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9
Q

What is cluster randomisation?

A

Unit of randomisation and analysis is various centers or catchment zones rather than individuals.

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10
Q

Significance of clusters in cluster randomisation

A

Within a cluster patients are more likely to respond in a similar manner and can therefore no longer be assumed to act as independent units.

Leads to loss of power

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11
Q

What is used in power calculations for cluster randomisations?

A

Effective sample size instead of actual sample size

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12
Q

What is used to calculate effective sample size?

A

Intracluster correlation

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13
Q

What does intracluster correlation represent?

A

Degree to which various individuals in a cluster resemble each other in outcome measure

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14
Q

Why is effective sample size needed in cluster randomisation?

A

People in a set cluster will act in a similar way to an intervention

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15
Q

When is minimisation randomisation useful?

A

When you want to do stratified randomisation due to worries of unequal distribution, but trial is too small to do so.
When conducting cluster randomisation and the clusters are small in number. You wish to minimise differences in confounder distribution

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16
Q

What can minimisation help do?

A

Achieve balance between treatment groups

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17
Q

What happens in minimisation?

A

Next allocation depends on characteristics of those already allocated

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18
Q

Advantages of minimisation

A

Ensures balance of prognostic factors between groups

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19
Q

Disadvantages of minimisation

A

Method is inferior to proper randomisation as allocation is exposed and controlled manually

Only first randomisation is truly random

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20
Q

Characteristics of sound randomisation

A

Reproducible order of assignment
Documented methods of assignment
Assignments remain concealed
Future assignments not predictable from past assignments
Ability to detect departures from established procedures

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21
Q

What is quasi randomisation?

A

Randomising using even/odd numbers of DOB/day of week patient was seen etc.

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22
Q

Problems of quasi randomisation

A

Not reproducible
Sequences cannot ensure equal distribution of variables

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23
Q

Advantages of randomisation

A

Permits use of probability theory in making inferences
Eliminates effects of bias
Facilitates blinding
Distributes baseline characters in unpredictable fashion
Improves generalisability

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24
Q

What does precision depend on?

A

Sample size

Not randomisation

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25
Q

Special types of RCTs

A

Crossover
N of 1
Factorial
Patient preference
Zelens modified
Non-inferiority

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26
Q

What is a crossover RCT?

A

Interchange of study and control groups after washout period so all subjects receive treatment and placebo

27
Q

Which diseases can crossover RCTs not be used for?

A

Diseases cured by use of medication

28
Q

What is parallel RCT?

A

Both control and intervention happen in parallel, not in serial fashion i.e. opposite of crossover

29
Q

What is N of 1 trial?

A

Single subject is administered placebo and intervention in tandem under double-blind controlled conditions.

30
Q

What is factorial trial?

A

In 2x2 factorial design, participants are allocated to one of four combinations (2 treatments, 2 levels).

31
Q

How many possibilities in a 2x2x2 trial?

A

3 treatments at 2 levels

32
Q

Advantage of factorial trial

A

Can test both independent effect of each drug and combined effect

33
Q

What are patient preference trials?

A

Patients may have strong preference for certain therapy, and are allocated to that one.
Only those with no preference are randomised.

34
Q

How can researcher obtain data from patients who have preferences in preference trials?

A

In parallel fashion

35
Q

Advantages of patient preference trials

A

Increased recruitment
One can analyse motivation on intervention effectiveness

36
Q

Disadvantages of patient preference trials

A

Recruiting for no preference can be more difficult
Obtaining consent canbe complex

37
Q

What is Zelens modified RCT?

A

Randomisation occurs before consent; consent only from those randomised to experimental treatment.

38
Q

Reason behind Zelens modified RCT?

A

In standard RCT, patients tend to withdraw if they suspect they are in the placebo group and not receiving treatment they hoped for.

39
Q

Disadvantages of Zelens modified RCT

A

Ethically controversial; MRC does not accept this design as ethically valid

40
Q

What are non-inferiority RCTs?

A

When aim is to show that new intervention is ‘‘not inferior’ to standard intervention

41
Q

What is null hypothesis of non inferiority RCTs?

A

There is significant difference between two interventions and not otherwise as seen in superiority trials

42
Q

Another name for non inferiority trials?

A

Equivalence trial

43
Q

Disadvantages of non inferiority trials

A

Higher sample size needed compared to superiority trial for same level of power and significance

Intention to treat analysis may blur differences between groups and may support claim of equivalence

44
Q

In which trials is it best to report both ITT and per-protocol analysis?

A

Non-inferiority

45
Q

Types of interventional trials

A

RCTs
Uncontrolled
Before and after
Multi arm

46
Q

What happens in uncontrolled trials?

A

Only one group observed for effects of intervention - no control.

47
Q

What is study inference made from in uncontrolled trials?

A

Using historical control i.e. status of treated group before intervention

48
Q

What happens in before and after trials?

A

Outcome is assessed before and after the intervention in one group of subjects.

49
Q

Weakness of before and after trial?

A

No randomisation
Observed change may be due to a factor other than intervention

50
Q

What is a multi arm trial?

A

RCT where there is more than one study arm.

51
Q

Disadvantages of multi arm RCT

A

Larger sample size so power may be reduced

52
Q

What happens to power as sample size increases?

A

Power reduces

53
Q

What is efficacy?

A

How well a drug works under optimal circumstances

54
Q

What is effectiveness?

A

How well drug works under usual practice circumstances

55
Q

What is efficiency?

A

Measures whether healthcare resources are being used to maximise value for money

56
Q

When is efficacy trial undertaken?

A

To meet regulatory approval

57
Q

When is effectiveness trial undertaken?

A

Convince formularies and payers of actual usefulness of drug in current practice

58
Q

What are pragmatic trials?

A

Effectiveness trials for which hypothesis and study design are designed to answer the questions faced by decision makers

59
Q

Unnatural circumstances in RCT compared to regular clinical practice

A

Recruitment from specialist centres
Exclusion of patients with co-morbidities
Careful selection of patients to generate homogenous diagnostic groups
Random allocation
Detailed information given for patient consent
Placebo used to compare active treatment
Patients followed up frequent intervals
Patients receive detailed checklist of SEs
Assessment endpoint is usually 4-6 weeks
Sx measures are outcomes considered
Patients + clinicians blinded

60
Q

Characteristics of pragmatic RCTs

A

Select clinically relevant alternative interventions to compare
Include diverse population of participants
Recruit participants from heterogenous practice settings
Collect data on broad range of health outcomes

61
Q

What do pragmatic RCTs tell you (and not tell you)?

A

Inform how effective intervention is in real world
Do not tell you how efficacious t is

62
Q

Problems with pragmatic RCTs

A

Substantial drop-out rates
Blinding can fail
Less rigorous methodology
Higher rates of non-specific treatment
May not employ placebos
May not be blinded
Must carefully conceal allocation during effects

63
Q

Advantages of pragmatic RCTs

A

Reflect heterogeneity of patients in clinical practice
Minimise exclusion criteria
Focus on groups with wide range of diagnoses
Define patient groups by presentation rather than diagnosis
randomisation
May evaluate real world, function based outcomes

MRCPsych Part B (64 decks)

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