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CPT > Clinical trials > Flashcards

Clinical trials Flashcards

1
Q

Define what a clinical trial is

A
  • Form of planned experiment
  • Involves patients and is designed to elucidate most appropriate method of treatment for future patients with a given medical condition
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2
Q

Define efficacy in the context of a clinical trial

A
  • Ability of a health care intervention to improve the health of a defined group under specific conditions
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3
Q

Define safety in the context of a clinical trial

A
  • Ability of a health care intervention not to harm a defined group under specific conditions
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4
Q

What are the different phases of a clinical trial?

A
  • Phase I: <100 healthy volunteers - checks for pharmacodynamics, pharmacokinetics, major side effects
  • Phase 2: <1000 patients - checks for effects and dosages, common side effects
  • Phase 3: <10 000 patients - comparison with standard treatments
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5
Q

What are the most important ethical considerations for any clinical trial to go ahead?

A
  • Trials of new drugs may do harm
  • You should only conduct a trial if you are in clinical equipoise
  • Patient/participants must understand what participation in the trial involves
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6
Q

Outline what equipoise means

A
  • If there are only a few choices for a drug then it is more ethical to do a trial
  • Trial will benefit patients by providing them with a treatment for their condition when few/no treatments currently exist
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7
Q

What do non-randomised clinical trials involve?

A
  • Allocation of patients receiving a new treatment to compare with a group of patients receiving standard treatment
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8
Q

How are patients allocated in a non-randomised clinical trial?

A
  • Allocation may be by:
  • Site
  • Historical controls
  • Simple system devised by investigator
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9
Q

What can allocation lead to in non-randomised clinical trials?

A
  • Allocation bias by patient, clinician, or investigator
  • Confounding - known and unknown
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10
Q

What does comparison with historical controls involve?

A
  • Comparison of a group of patients who had standard treatment with a group of patients receiving new treatment
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11
Q

What are the problems with using historical controls in clinical trials?

A
  • Selection often less well defined, less rigorous
  • Treated differently from new treatment group
  • There may be less information about potential bias/confounders
  • Unable to control for confounders
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12
Q

Why is randomisation ideal?

A
  • Eliminates allocation bias, giving each participant an equal chance of being allocated to each of the treatments in the trial
  • Minimal confounding, leading to treatment groups that are likely to be similar in size and characteristics by chance
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13
Q

What is a confounder?

A
  • A factor associated with the exposure and is independently a risk factor for the disease
  • This association is separate to the relationship between risk factor being investigated
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14
Q

How should randomisation be carried out?

A
  • Should use concealed allocation so there is no possibility of predicting allocation of next patient
  • Randomisation sequence should be prepared by someone who is not entering patients and allocation should be at a distance
  • E.g. use a third party
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15
Q

How do we do randomisation?

A
  • Normally use a 3rd party, computer generated random allocation, accessed by phone/internet
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16
Q

What does a clinical trial need to be in order to give a fair comparison of effect and safety?

A
  • Reproducible - in experimental conditions
  • Controlled - comparison of interventions
  • Fair - unbiased without confounding
  • Differences observed in small trials are more prone to chance
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17
Q

How might knowledge of which participant is receiving which treatment bias the results of a clinical trial?

A
  • Patient may alter behaviour, other treatment, or even expectation of outcome (behaviour effect)
  • Clinician may alter their treatment, care and interest om patient (non-treatment effect)
  • Investigator may alter their approach when making measurements and assessing outcomes (measurement bias)
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18
Q

What is a single blind trial?

A
  • Either patient, clinician, or assessor does not know treatment allocation (usually patient)
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19
Q

What is a double blind trial?

A
  • Two of patient, clinician or assessor does not know treatment allocation
  • Usually patient + assessor/clinician
20
Q

Give examples of how blinding/masking might be carried out?

A
  • Aim to make treatments appear identical in every way e.g. appearance, taste, texture, dosage regimen, warnings
  • Use a designated pharmacy to label identical containers for the treatments with code numbers to differentiate between them
21
Q

When might blinding be difficult?

A
  • Surgical procedures
  • Psychotherapy vs antidepressants
  • Alternative medicine vs Western medicine
  • Lifestyle interventions
  • Prevention programmes
22
Q

What does randomisation eliminate in a trial?

A
  • Confounding
23
Q

What does good randomisation eliminate in a trial?

A
  • Selection bias
24
Q

What does blinding eliminate in a trial?

A
  • Outcome measurement bias
25
Q

How do we determine who should or shouldn’t take part in a clinical trial?

A
  • Inclusion criteria
  • Exclusion criteria
  • E.g. age, sex, health
26
Q

Why do we pre-define outcomes in clinical trials?

A
  • Prevent data dredging, repeated analyses
  • Have a clear protocol for data collection
  • Agreed criteria for measurement and assessment of outcomes
27
Q

What is meant by pre-defining outcomes in clinical trials?

A
  • Need to define what, when and how outcomes are to be measured before the start of the clinical trial
28
Q

Define primary and secondary outcomes

A
  • Primary outcome: preferably only one primary outcome, used in sample size calculation
  • Secondary outcomes: other outcomes of interest, often includes occurrence of side-effects
29
Q

What are the types of outcomes in a clinical trial?

A
  • Pathophysiological e.g. tumour size, thyroxine level, other biomarkers
  • Clinically defined e.g. death, disease, disability
  • Patient focused e.g. quality of life, psychological well-being, social well-being, satisfaction
30
Q

What are the features of an ideal outcome?

A
  • Appropriate and relevant
  • Valid and attributable - any observed effect can be reasonably linked to treatments being compared
  • Sensitive and specific - changes detected accurately
  • Reliable and robust - similar results obtained by different people in various settings
  • Simple and sustainable
  • Cheap and timely
31
Q

When should we monitor clinical trials?

A
  • Need to monitor inadvertent differences in groups
  • Monitor outcomes during trial
  • Possible effect - is one group being disadvantaged
  • Adverse effects - are patients being harmed
  • Final measurement of outcomes - compare final effect of treatments in trial
32
Q

How do we show comparability between groups?

A
  • Ensure that groups compared are as equivalent as possible
  • Collecting baseline data on characteristics that we think may relate to both condition and outcomes we are investigating
33
Q

Define the placebo effect

A
  • Even if the therapy is irrelevant to the patient’s condition, the patient’s attitude to their illness and the illness itself may be improved by a feeling that something is being done about it
34
Q

What is a placebo?

A
  • Inert substance made to appear identical in every way to active formulation to which it is compared
  • E.g. appearance, taste, texture, dosage, regimen, warnings etc.
35
Q

What is the aim of a placebo?

A
  • Cancel out any placebo effect that may exist in active treatment
36
Q

What are the ethical implications of placebo?

A
  • Placebo should only be used when no standard treatment is available
  • Use of a placebo is a form of deception
  • Essential that participants in a placebo-controlled trial are informed that they may receive a placebo
37
Q

Why might we lose participants from a clinical trial?

A
  • Clinical condition may necessitate their removal from trial (appropriate)
  • Participant may choose to withdraw from trial (unfortunate)
38
Q

How do we minimise losses to follow up?

A
  • Make follow-up practical and minimise inconvenience
  • Be honest about commitment required from participants
  • Avoid coercion or inducements but can recompense participants for their time/trouble
  • Maintain contact with participants
39
Q

Why might participants not adhere to treatment during clinical trials?

A
  • May have misunderstood instructions
  • May not like taking their treatment
  • May think treatment is not working
  • May prefer to take another treatment
  • Can’t be bothered to take treatment
40
Q

How can we maximise adherence with treatments?

A
  • Simplify instructions
  • Ask about adherence
  • Ask about effects and side effects
  • Monitor adherence e.g. tablet count, urine level, blood level
  • Never possible to achieve 100% adherence
41
Q

How can we tell if a new treatment is better than the standard treatment?

A
  • Is the physiological action of the new treatment better than the standard treatment
  • Is the new treatment better than the standard treatment in routine clinical practice
42
Q

What are the pros and cons of ‘as-treated’ analysis?

A
  • Analyses only those who completed follow-up and adhered to treatment
  • Compares physiological effects of treatments
  • But loses effects of randomisation
  • Non-adherers likely to be systematically different from those adhering to treatment
  • Leads to selection bias and confounding
43
Q

Outline intention to treat analyses

A
  • Analyses according to original allocation of treatment groups
  • Regardless of whether participants completed follow-up or adhered to treatment
  • Compares likely effects of using treatments in routine clinical practice
  • Also preserves effects of randomisation - minimal selection bias and confounding
44
Q

Compare as-treated with intention to treat analyses?

A
  • As treated analyses tend to give larger sizes of effect
  • Intention to treat analyses tend to give smaller and more realistic sizes of effect
  • Clinical trials should normally be analysed on an intention to treat basis
45
Q

Outline the steps involved in a RCT

A
  1. Disease of interest
  2. Is it ethical?
  3. Methods of group allocation and blinding
  4. Patients eligible for trial
  5. Patients to be excluded from trial
  6. Baseline data collection (demonstrate group comparability)
  7. Outcomes to be measured
46
Q

Outline what steps need to be taken in order to conduct a RCT

A
  1. Identify a source of eligible patients
  2. Invite patients to participate
  3. Obtain consent
  4. Allocate participants to treatments fairly
  5. Follow up participants in identical ways
  6. Minimise losses to follow-up
  7. Maximise adherence with treatments
47
Q

Outline the steps taken to analyse comparison of outcomes from a RCT

A
  1. Is there an observed difference in outcome between treatment groups
  2. Is it statistically significant (or due to chance)
  3. Is the observed difference clinically important
  4. Is the observed difference attributable to the treatments compared in the trial

CPT (22 decks)

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