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Biostatistics > 5 - Clinical trials > Flashcards

5 - Clinical trials Flashcards

1
Q

Difference b/w clinical trials & controlled lab investigations

A
  • Ethics → experiment involving human subjects ?!

- Bias → “ on intelligent subjects requires new measures of control

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2
Q

What is the hierarchy of scientific evidence?

A

case reports –> case series –> ecologic studies
–> cross-sectional studies –> case-control studies –> cohort studies –> RANDOMISED CONTROLLED TRIALS

(from generating hypotheses to establishing causality)

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3
Q

How is a hypothesis formed?

A
  1. Primary Q
    Eg: “In population X, is drug A at daily dose Y more efficacious in reducing K, over a period of time T, than drug B at daily dose Z?”
  2. Secondary Q
    Study-related Qs in the whole gp or its subgroups
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4
Q

Which 2 groups are compared in a study?

A

Treatment gp = allocated the agent under study
Comparison gp = not allocated the agent under study
(may receive no treatment, an inactive treatment aka PLACEBO or another active treatm (e.g standard treatm))

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5
Q

Types of study designs

A
  1. Simple randomised design
  2. Stratified randomised design
  3. Crossover design
  4. Factorial design
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6
Q

What is the basis of stratified randomised studies?

A

If prognostic factors are known & pts can be grouped into prognostic categories, comparability among treatm gps is better achieved w/ stratification
Within each gp, pts are randomly assigned to treatments

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7
Q

What is the basis of crossover studies?

A

Pts serve as their own controls

Eg: subjects may undergo therapy for 6w & then “cross over” to control therapy for another 6w

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8
Q

What is a -ve of crossover study design?

A

potential for “carryover” effects (i.e treatm given during 1st period may carry over into 2nd period)

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9
Q

What are the types & what is the basis of factorial studies?

A

Motive = ask 2 or + Qs in same clinical trial

  • 2x2 –> simplest factorial design: 2 treatments studied for their relationship to response & each is given at 2 levels (eg high dosage & low dosage or drug A & B)
  • 2x2x2 etc
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10
Q

The 5 elements of research protocol

A
  1. Sample size
  2. Funding
  3. Approval from ethics committee
  4. Eligibility criteria
  5. Signed informed consent
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11
Q

What are the main parameters of sample size estimation?

A
  • Level of significance/ α → how big a risk can be taken that the 2 treatm are incorrectly shown as statistically different?
    p Β error & 1-β (power of a trial)→ how “ “ “ as not statistically different?
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12
Q

Randomisation is the preferred method of assigning pts to receive treatments being compared. True or false?

A

True

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13
Q

What are the 3 main randomisation methods?

A

Method 1: toss a coin
Method 2: use a table of random numbers
Method 3: stratified block randomisation

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14
Q

What are the +ves of randomization?

A
  • Produces study gps comparable w/ respect to known & unknown risk factors
  • Removes investigator bias in allocation of participants & guarantees results have valid significance
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15
Q

What is the purpose of a placebo?

A

match experience of comparison gp w/ that of treatm gp

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16
Q

What is blinding/masking (bias control) ?

A

= keeping identity of treatm masked for:

  • Subject → single-blind
  • Subject + investigator → double-blind
  • Triple-blind → extension of double-blind → committee monitoring response is not told identity of gps, simply given data for groups A & B
17
Q

What is the purpose of blinding/masking?

A

bias reduction

18
Q

What may adversely affect follow-ups?

A

pts dropout, or cant be located/contacted → lost to follow-up

19
Q

What are the reasons for non-compliance & the consequences?

A

Adverse reactions, waning interest, desire for other therapies

Consequences: smaller diff b/w treatm & comparison gps than truly exists → dilutes real impact of a treatm

20
Q

What can be done to prevent non-compliance?

A
  • Simple & easy-to-follow regimen
  • Present realistic pic of req tasks during consent process
  • Frequent contact w/ participants
  • Run-in period before enrollment & randomization
21
Q

What is the run-in period?

A
  • To ascertain which potential participants can comply to study regimen
  • Only compliant ppl are enrolled in trial
22
Q

What is an interim analysis?

A

Compares intervention gps at any time before formal completion of trial

23
Q

What is an ITT (intention-to-treat) analysis?

A

A specific strategy for generating results of a randomized trial
All subjects are compared in treatm gps to which they were originally randomized, regardless of any treatm they later received

(more informative & gives results closer to those that would’ve been seen if the treatm were given to the pop as a whole)

24
Q

Main advantages of ITT analysis

A

Preserves strengths of randomization, i.e minimize bias

Captures what happens in real-life

Gives a pragmatic estimate of effect of a treatm

25
Q

Main limitations of ITT analysis

A
  • Includes data from both compliant & non-compliant subjects + those who switch treatm gps unexpectedly
  • Does not determine max potential effectiveness (unlike PP analysis)
  • Same or less statistically significant benefit than PP
  • May be no more effective than placebo
26
Q

What is a PP (Per-protocol) analysis?

A
  • Aka efficacy analysis or analysis by treatm administered

- Exclude subjects who were not fully complaint w/ protocol

27
Q

What are the key points concerning ITT & PP analysis?

A

ITT:

  • Provides unbiased assessment of treatm, usually preferred
  • Accounts for treatm effects, difficulties in administering the drug, compliance issues

PP:
- Evaluates max benefit from a treatm (given perfect compliance)

28
Q

What are the 6 different types of clinical trials?

A
  1. Prevention trials
  2. Screening trials
  3. Diagnostic trials
  4. Treatment trials
  5. Quality of life trails (supportive care trials)
  6. Compassionate use (or expanded use) trials
29
Q

What are the 4 clinical trial phases?

A

Phase 1: clinical pharmacology & toxicity
Phase 2: initial clinical investigation for treatment effect
Phase 3: full-scale evaluation of treatment (clinical trial)
Phase 4: post-marketing studies

30
Q

State the objective, design & subjects of phase 1 clinical trials.

A

Objective - determine a safe drug dose for further studies of therapeutic efficacy

Design - dose-escalation to establish a max tolerated dose (MTD) for a new drug

Subjects - 1-10 normal volunteers or pts w/ dx

31
Q

State the objective, design & subjects of phase 2 clinical trials.

A

Objective - to get preliminary info on effectiveness & safety of drug

Design - often single arm (no control gp)

Subjects - usually 10-100 pts w/ dx

32
Q

State the objective, design & subjects of phase 3 clinical trials.

A

Objective - compare efficacy of new treatm w/ standard regimen

Design - randomized controlled

Subjects - usually 100-1000 pts w/ dx

33
Q

State the objective, design & subjects of phase 4 clinical trials.

A

After drug approved for market → monitoring of side effects & long-term + large-scale studies of morbidity & mortality (e.g thalidomide)

Objective - to get more info (long-term side effects)

Design - no control gp

Subjects - pts w/ dx using the treatm

Biostatistics (15 decks)

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