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2º Parcial RM > Trials > Flashcards

Trials Flashcards

1
Q

Experimental studies are the best methods to

A

Support cause-effect relationships

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2
Q

Differences with observational studies

A

Researcher introduces / manipulates the exposure

Much more validity if the assignment of the exposure is random and the sample size sufficiently large

Exposure doesn’t exist before starting the trial

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3
Q

Disadvantages of the experimental studies

A

Can only answer very limited range of questions (strict rules, no variability) about variety of doses, combinations of doses / exposures, long-term exposures, special effects in subgroups of peculiar patients

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4
Q

Features of experimental studies

A

Last steps in research
Measure efficacy (ideal circumstances) not effectiveness (real circumstances)

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5
Q

Types of trials

A

Clinical trials
Field trials
Cluster trials

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6
Q

Clinical trials

A

Participants randomly allocated are patients with a previous disease

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7
Q

Field trials

A

Participants are initially free of disease

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8
Q

Cluster trials

A

The unit of randomization is a group (it should be a large number size)

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9
Q

Phase I trials tests

A

If a new treatment is safe and look for the best way to give it

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10
Q

Phase I trials focus

A

Safety and tolerance

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11
Q

Phase I trials participants

A

20-80 healthy volunteers

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12
Q

Phase I trials features

A

No control group

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13
Q

Phase II trials test

A

Response of the disease to a new treatment

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14
Q

Phase II trials provide

A

Preliminary information on efficacy, dose-response and add information on tolerance

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15
Q

Phase II trials participants

A

100-200 patients with disease

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16
Q

Phase IIa trials

A

Pilot study
Small sample
Healthy and diseased

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17
Q

Phase IIb trials

A

Usually controlled
Test efficacy
Only patients

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18
Q

Phase III trials test

A

Is a new treatment is better than a standard one

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19
Q

Phase III trials provide

A

The definitive answer for efficacy and safety

20
Q

Phase III trials features

A

Large sample size
Needs sufficient duration
Always controlled
Randomized
In medical journals

21
Q

Phase IV trials provide

A

Information about long-term benefits and side effects

22
Q

Phase IV trials features

A

Post-marketing

23
Q

Designs of clinical trials

A

Cross-over trials
Factorial design

24
Q

Cross-over trials

A
25
Q

Factorial design

A
26
Q

Aim of clinical trials

A

Explanatory / pragmatic trials
Superiority / equivalence / non-inferiority trials

27
Q

Explanatory trials

A

Strict inclusion criteria
Ideal setting of “experimental” conditions

28
Q

Pragmatic trials

A

Wide (lax) inclusion criteria
Real conditions

29
Q

Superiority trial

A

Refutation of null hypothesis (both treatments are equal) leads to the conclusion that one of them is superior

30
Q

Equivalence trial

A

Demonstrate that A and B are equal (efficacies are close enough from a clinical / practical point of view)

31
Q

Non-inferiority trials

A

Demonstrate at least same efficacy
Only look to one bound of CI
One-tailed tests

32
Q

Placebo effect

A

Sum of non-specific effect of the physician, non-specific effect of the drug and regression to the mean

33
Q

Distingish placebo effect from pharmacodynamic effect

A

This makes it possible to substract the placebo effect from the efficacy attributed to the treatment being evaluated.

34
Q

Randomization

A

Assigning participants to the different study groups by a random (unpredictable) mechanism

35
Q

Randomization of a large number of subjects tend to produce

A

Identical groups with respect to known characteristic as well as unknown characteristics

36
Q

The only between-group difference in randomized groups will be

A

Intervention to which subjects have been assigned -> all differences in outcomes will be specifically due to that intervention = strong causal inference

37
Q

Features of randomization

A

Gold standard for showing causality
Eliminates biased assignment of treatments
Facilitates blind evaluation of the outcomes
Allows statistical test that assume randomly distributed differences under the null hypothesis

38
Q

Conditions for randomization

A

Sufficient large sample size
Truly random assignment method
Masking of the random sequence (MRS)

39
Q

Ransom sampling vs random allocation (randomization)

A

Random sampling: small subset (sample) is selected (drawn)

Random allocation: all the study subjects are distributed in groups

40
Q

Problem in randomization

A

Conflict emerges between the clinician’s role and the aim of a clinical trial, and as a result, unintentional biases may occur: clinicians may be tempted to cheat (to help patients)

41
Q

Restricted randomization

A

Random allocation can be made in blocks -> keep sizes of groups similar

Stratified randomization: 1º stratifying the whole study population into subgroups with the characteristics (strata) then simple random sampling from the stratifies groups

42
Q

Masking of the random sequence (MRS)

A

Does not allow to guess to know what group will go the next patient (unpredictability).

This is done at the beginning of the trial.

43
Q

Blinding of the intervention when assessing outcomes (BIWAO)

A

Investigators responsible for assessing or adjudicating the outcomes do not know the allocated group.

Particularly important when assessing subjective outcomes (pain or anxiety)

44
Q

Intention to treat (ITT)

A

Analysis of the results of the trial that follows the initial random group assignment

Resembles the reality of clinical practice where patients not always comply

Biases the results towards the null value (potential benefit underestimated)

45
Q

Per protocol (P-P)

A

Analysis that only includes compliers (advantage of randomization is eliminated

Any difference tends to be exaggerated

Better for equivalence studies

46
Q

Integrim vs subgroup

A

Interim: repeated provisional analyses meanwhile the trial is on-going

Subgroup: analyses only including a subset of participants. If the effect is not present in the overall sample, there is not much justification to defend the effect within a subgroup

Both require lower p values (instead of p<.05) for achieving statistical significance.

47
Q

Important consideration for randomized trials

A

Despite their high internal validity they have low external validity (low ability to generalize their results)

2º Parcial RM (8 decks)

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