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Block 3 > Study Designs 2 - RCTs > Flashcards

Study Designs 2 - RCTs Flashcards

1
Q

What is a clinical trial?

A

A scientific way of testing a clinical question by comparison with control group

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2
Q

What might you want to assess in a clinical trial?

A 
Treatments
Supportive care
Devices
Screening programmes
Information
Diagnostic tests
Biomarkers
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3
Q

What key lessons have we learnt in history from clinical trials?

A
  1. James Lind & Scurvy: orange + lemons have the best effect when everything else was kept constant
  2. Gold therapy for TB: controls had better improvement
  3. Natural history of disease + vaccine therapy: no better than placebo
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4
Q

What have lessons from history taught us?

A
  • Collect data i.e. dont rely on anecdotal evidence
  • Need for controls
  • Avoids bias - groups should be comparable except for treatment
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5
Q

What principles must be followed when comparing treatment groups?

A
  • Groups alike in all important aspects except for treatments under evaluation getting rid of possible bias
  • Large enough sample to limit chance imbalance
    = difference in outcome is just due to treatment effect
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6
Q

Why use randomisation?

A

Best way to create a CONTROL group similar to the TREATMENT group in all respects (known and unknown)

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7
Q

What is a randomised clinical trial (RCT)?

A

Controlled clinical trial where therapies allocated by a chance mechanism where neither patient nor physician knows in advance which therapy will be assigned

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8
Q

What are the advantages of randomised clinical trials (RCTs)?

A
  1. Eliminate selection bias
  2. Balance prognostic factors
  3. Validity of statistical tests
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9
Q

What is a controlled clinical trial?

A

Prospective study comparing effects and value of an intervention against a control in human subjects

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10
Q

What is an uncontrolled clinical trial?

A

Involves NO control group

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11
Q

What is the main dictator of how good a study design is?

A

Reducing bias to an absolute minimum

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12
Q

In order of worst to best, what types of studies have the best study design?

A
  1. Uncontrolled
  2. Historical controls
  3. Current non-randomised controlled
  4. Randomised controlled
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13
Q

What is the concept of statistical interference?

A

Analysed data are results in a selected sample and we use these results to infer how all the population would behave - start with pop. and get protocol treated patients, look at observed results and extrapolate then:
- Estimate: treatment effect (beware bias)
- Beware of variability of estimate due to sampling from population
= Goal: control bias + reduce variability

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14
Q

What is the benefits of random allocation of treatment?

A
  • Gives equal chance of receiving each treatment
  • In long run leads to groups likely to be similar in characteristics by chance
  • Reduces selection bias if patients enter trial before randomisation
  • Used in other experimental settings
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15
Q

What is the placebo effect?

A

Even if therapy is irrelevant to the patients condition, the patients attitude to his or her illness, and indeed the illness itself, may be improved by a feeling that something is being done about it

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16
Q

A difference between results of treatment and no treatment group could be one of 2 things, what are these?

A
  1. True treatment effect

2. Placebo effect as one group is receiving care

17
Q

What is the aim of blind trials?

A

Aims to remove differential placebo effect that could bias comparison between treatments i.e. strengthening randomisation

18
Q

What is a single blind trial?

A

Where one of patient, clinician or assessor does not know the treatment allocation - usually PATIENT

19
Q

What is a double blind trial?

A

2 or more of patient, clinician or assessor does not know the treatment allocation - usually PATIENT and CLINICIAN/ASSESSOR

20
Q

Give some examples of blinding.

A
  1. Make treatment appear identical in taste, appearance, texture, dosage, regime etc.
  2. Compare active drug with placebo (inert substance identical in appearance, taste, texture etc.)3. Use a designated pharmacy to label identical containers with code numbers
21
Q

How is a trial conducted?

A
  1. Eligible patient presents
  2. Consents
  3. Randomised to either new or control treatment
  4. Assessment
22
Q

How are trial outcomes evaluated?

A

Compare the outcomes fairly to see:

  • Is there a difference between groups?
  • Could the difference have arisen by chance or is it statistically significant?
  • How big is the difference, is it clinically important?
  • Is the difference attributable to treatments in the trial?
23
Q

Why might participants not remain in the trial?

A
  • Clinical condition may necessitate removal from trial

- May chose to withdraw

24
Q

Why might participants not comply with allocated treatment?

A
  • Misunderstood instructions
  • May not like taking treatment
  • May think its not working
25
Q

Why do we want to keep patients in trials?

A

So data is not skewed or bias i.e. if a patient is removed due to treatment affecting them negatively, if they are removed along with all their data this wont be recorded

26
Q

How can we increase compliance?

A
  • By giving medicines in chunks e.g. 2-weekly doses rather than 6-montly
  • Give them incentives e.g. group exercises
  • Make goals realistic e.g. for obesity and exercise
27
Q

How are patients randomised?

A

Either to NEW treatment (either take new treatment or not) OR STANDARD treatment (take control treatment or not)

28
Q

How can be determine if the new treatment is better than the standard?

A

2 different interpretations:

  1. Is the PHYSIOLOGICAL ACTION of the new treatment better than the standard?
  2. Is new treatment better than standard treatment IN ROUTINE CLINICAL PRACTICE?
29
Q

What is an explanatory trial?

A

I.E. ‘as-treated’ analysis where you compare just the patients that have taken the new treatment with those that have taken the control treatment - those who completed follow-up and complied with treatments comparing physiological effects of treatment - tend to give larger sizes of effect

30
Q

What is the disadvantage of an explanatory trial?

A

Loses effect of randomisation as non-compliers are likely to be systemically different from compliers so there is selection bias and confounding

31
Q

What is a pragmatic trial?

A

I.E. ‘intention-to-treat’ analysis where both groups in the new and standard treatment groups are compared - tend to give smaller effect sizes and reflect effect in clinical practice

32
Q

What type of analysis is best used for definitive clinical trials?

A

‘Intention-to-treat’ basis

33
Q

What is the ethical dilemma of clinical trials?

A

Clinician should provide best treatment for each individual patient but scientific integrity requires treatment chosen randomly so can these requirements be reconciled?

34
Q

What is clinical equipoise?

A

Where reasonable uncertainty about which treatment (including non-treatment) is better when putting a patient into trials so randomisation does not deny any patient the best treatment - the only qualification is ignorance

35
Q

What should be explained to the patient when gaining informed consent for a trial?

A
  • That the patient is invited to be in a trial
  • What the alternative treatments are (including known side effects)
  • That treatment will be allocated at random
  • That patients may withdraw at any time
36
Q

How should informed consent information be given?

A

Verbally and in writing with a ‘cooling off’ time for patients to think and reflect about the information (24hrs) by a knowledgeable informant

37
Q

What process does standard randomisation use?

A
  1. Are patients eligible?
  2. If yes, patient consent
  3. If they dont consent, drop them from trial
  4. If they consent, randomise to treatment A or B
38
Q

What process does the Zelen method use?

A
  1. Are patients eligible?
  2. If yes, randomise
  3. No consent is needed for standard treatment A
  4. Seek consent
  5. If consent is given, give treatment B
  6. If consent is not given, give standard treatment A
39
Q

Why might the Zelen method be beneficial to use?

A

Because when giving a patient all information about a trial for informed consent, they may end up in the non-treatment group knowing that are missing out on treatment - this method avoids this as the non-treatment group do not need to be informed or give consent

Block 3 (40 decks)

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