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Research & Stats > Week 11- Interventional Studies > Flashcards

Week 11- Interventional Studies Flashcards

1
Q

OVERALL DIAGRAM

A
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2
Q

TIMELINE DIAGRAM

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3
Q

What are experimental (intervention) studies?

A

– Investigator completely controls exposure
* type, amount, duration, and
* who receives it (randomization)
– Can confidently attribute cause and effect due to
prospective designs and the high internal validity of trials
– Trials are not always feasible, appropriate, or ethical

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4
Q

Why is experimental studies regarded as the most scientifically vigorous study design?

A
  • Random assignment reduces confounding bias
  • Concealment reduces selection bias
  • Blinding reduces biased measurement (information bias)
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5
Q

What are prophylactic trials?

A

Evaluate efficacy of intervention
designed to prevent disease, e.g., vaccine, vitamin
supplement, patient education

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6
Q

What are treatment trials?

A

Evaluate efficacy of curative drug or
intervention or a drug designed to manage signs and
symptoms of a disease (e.g., arthritis, hypertension)

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7
Q

What are RCT trials?

A

Individuals, tightly controlled, narrowly
focused, highly select groups, short or long duration

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8
Q

What are community/ cluster trials?

A

Cities/regions/schools/hospitals, less rigidly controlled,
long duration, usually primary prevention

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9
Q

How many clinical trial phases are there?

A

4

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10
Q

What does phase 1 include?

A

Researchers test a new drug or treatment in
a small group of people for the first time to evaluate
its safety, determine a safe dosage range, and
identify side effects (no control group is included)

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11
Q

What does phase 2 include?

A

The drug or treatment is given to a larger
group of people to see if it is effective (outcome
assessment) and to further evaluate its safety (no
control group is included)

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12
Q

What does phase 3 include?

A

The drug or treatment is given to large
groups of people to confirm its effectiveness,
monitor side effects, compare it to commonly used
treatments or placebo, and collect information that
will allow the drug or treatment to be used safely
CONTROL GROUP

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13
Q

What does phase 4 include?

A

Studies are done after the drug or
treatment has been marketed to gather information
on the drug’s effect in various populations and any
side effects associated with long-term use

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14
Q

What is a randomised controlled trial (RCT)?

A
  • RCT is a study in which participants are assigned to a
    study group
  • Procedures are controlled to ensure that all participants
    in all study groups are treated the same except for the
    intervention that is unique to their group
  • Assigned to treatment conditions at random (i.e., they
    have an equal probability of being assigned to any
    group)
  • Study groups are also called study arms or treatment
    conditions
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15
Q

Why is randomisation important?

A
  1. Random assignment ensures that known and
    unknown person and environment characteristics that
    could affect/distort the outcome of interest are evenly
    distributed across groups => control for known and
    unknown confounders
  2. Gives the investigator confidence that differences in
    outcome between treatment and control were
    actually caused by the treatment, since random
    assignment (theoretically) equalizes the groups on all
    other variables
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16
Q

What does Allocation Concealment mean?

A

Allocation concealment means that the person who
generates the random assignment remains blind to what
condition the person will enter

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17
Q

Why is allocation concealment important?

A

If allocation is not concealed, research staff is prone to
assign “better” patients to intervention rather than
control, which can bias the treatment effect upward by
20-30%

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18
Q

What is blinding?

A
  • In blinding, the researchers collecting data are prevented
    from knowing certain information about a participant
    (e.g., what treatment arm they are in) in order to prevent
    this information from affecting how they collect data
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19
Q

What is double-blinding?

A
  • Ideally, to minimize information bias, both the participant
    and the investigator should be kept blind to
    the participant’s random assignment. That level of
    double-blinding may or may not be feasible.
  • Investigators should implement the greatest level of
    blinding that is feasible
20
Q

What are the 2 types of groups in RCTs?

A
  1. Intervention group= receives treatment of interest
  2. Control group= receives placebo/another treatment
21
Q

What is a placebo?

A

A Substances (usually a pill) identical to intervention substance, but LACKS THE ACTIVE INGREDIENTS (chemically inert)

22
Q

What is the placebo effect?

A

The placebo effect is a largely beneficial psychological effect of receiving treatment which comes from:
1. Patient’s beneficial response to investigation (incl. response to therapeutic ritual)
2. Patient’s beneficial response to observation and assessment
3. Patient’s beneficial response to patient-doctor interaction

23
Q

What is the goal of Placebo-controlled trials?

A

Allows for the study of effectiveness of intervention treatment BEYOND PLACEBO EFFECTS

24
Q

What is masking of placebo?

A

The same appearance, size, colour, taste (or even side effects) for active and placebo drug to reduce bias

25
Q

What are double blind trials?

A

-This level of blinding reduces the influence of expectations
held by participants or by research staff about which
treatment will have a better effect on the outcome.
-Double-blinding is most feasible for drug trials, in which the
effect of a medication is being compared to a placebo that
looks similar

26
Q

What else can the control group be except for placebo group?

A

RCTS can have several intervention groups and may not have a placebo group
1. If new treatment is being compared to old/ conventional treatment (OLD TREATMENT ACTS AS CONTROL)
2. If different dosages of a single treatment is being compared (CONTROL GROUP IS THE LOWEST DOSE)

27
Q

What is partial blinding?

A
  • Double-blinding is rarely possible in trials of
    behavioral treatment. It is usually obvious to
    participants which treatment they are receiving but
    the assessor of the outcome may be blinded to that
    information
  • Even if the treatment assignment is known by the
    research staff who delivers the treatment, the staff
    who assess the study outcome can and should be kept
    blind to the patient’s treatment condition.
    – Special care is needed to prevent staff and study
    participants from unblinding the outcome assessor
28
Q

What are unblinded trials?

A
  • Especially when neither participant nor
    investigator can be blinded, it is best if participants
    and research staff hold equally positive
    expectations about the merits of the treatment
    and control conditions.
    – The state of equipoise, uncertainty about which
    intervention condition will work best, is also the ethical
    justification for conducting a trial.
29
Q

Why is blinding important?

A
  • It is as important as randomization because it prevents
    – Biased assessment of outcomes post-randomization
    (i.e., measurement or ascertainment bias)
  • Blinding also helps reduces non-compliance and
    contamination
  • Blinding is particularly important if we have “soft”
    outcomes
    – e.g., self-report, investigator opinion
  • Sometimes blinding is not possible (= Open trial). If so,
    – Choose a “hard” outcome e.g. levels of CRP, lipids
    – Standardize treatments as much as possible
  • Blinding may be hard to maintain e.g., when obvious
    side effects are associated with a drug
30
Q

What is the difference between randomisation and random sampling?

A

Randomization should not be confused with random
sampling! Random sampling refers to recruiting a sample from
the source population into the study; if this sampling is not
random then the study will be prone to selection bias.

31
Q

What is the difference between blinding and allocation concealment?

A

Blinding should not be confused with allocation
concealment! Allocation concealment takes place before and
during participant allocation to intervention/control group,
whereas blinding occurs after participant allocation (i.e. during
study conduct – collection of outcome measurements).

32
Q

BASIC DESIGN OF RCT DIAGRAM

A
33
Q

MAIN PROBLEMS IN RCTs

A
34
Q

What are the 3 main problems in RCTs?

A
  1. Loss to follow-up
  2. Non-compliance
  3. Contamination
35
Q

Why would patients be lost to follow-up?

A

Side effects, moved, died, recovered, got worse,
lost interest

36
Q

What is the consequences of loss-to-follow-up, non-compliance and contamination?

A

– major bias
– decreased power
– and loss of credibility

37
Q

Why would patients be lost to poor compliance?

A

Side effects, iatrogenic reactions, recovered, got
worse, lost interest

38
Q

Why would patients be lost to poor compliance?

A

Contamination= cross-over
ESPECIALLY IN CONTROL GROUPS IF UNBLINDED

39
Q

How can we maximise FU and compliance?

A

By using:
1. two screening visits prior to enrollment
2. pre-randomization run-in period using placebo
or active drug
3. maintain blinding

40
Q

RANDOMIZED CROSS-OVER DESIGN DIAGRAM

A
41
Q

What are the advantages and disadvantages of Randomized Cross-over design?

A
  • Advantages: each subject acts as his or her own control, and smaller
    number of patients are required in comparison to parallel-group studies
  • Disadvantages: longer duration than parallel-group studies & difficulty for
    multiple dosage arms and with in dealing with drop-outs
42
Q

What are non-randomized and non-controlled trials?

A
  • Sometimes allocation of participants in each treatment group
    is not a result of randomization; in such a case the study is
    said to be a non-randomized trial
  • Sometimes clinical trials can take place in a single
    intervention group, with the lack of a control group; in such a
    case the study is said to be a non-controlled trial
  • Both of the above approaches should be avoided, as the
    likelihood of bias and confounding increases substantially
43
Q

What are Quasi-experimental designs?

A
  • A type of non-randomized design
    *In quasi-experimental designs, participants are
    assigned to a study condition using some nonrandom (but systematic) procedure
  • i.e., month of birth, every 2nd patient who comes,
    etc
44
Q

What are the advantages of RCT designs?

A
  • Measures efficacy and safety of an intervention
  • High internal validity: Able to control selection,
    confounding and measurement biases
  • Prospective – Incidence study – cause-effect
45
Q

What are the disadvantages of RCTs?

A
  • They are time- and energy- intensive (Phase I - III)
  • They are expensive
  • They may not be feasible for all interventions or
    settings
  • Not good for rare outcomes (as cohort studies)
  • The ability to make valid inferences (internal and
    external validity) depends on how well the
    investigator designed, conducted, and reported
    various procedures to minimize bias in the study
46
Q

SUMARRY OF RCTs

A
  • The key methodological components of an RCT are
    (1) use of a control condition to which the
    experimental intervention is compared; and
    (2) random assignment of participants to conditions
  • Random assignment reduces confounding bias
  • Concealment reduces selection bias
  • Blinding reduces biased measurement
  • Limitations: contamination, loss to FU, noncompliance
    FU=Follow-Up

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