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MPH > Clinical Trials (Midterm) > Flashcards

Clinical Trials (Midterm) Flashcards

1
Q

Definition of a clinical trial

A

A prospective study comparing the effect and safety of interventions against a control in human beings

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2
Q

What term is synonymous with “clinical trials”

A

“Randomized controlled trials”

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3
Q

What are phase I studies?

A

Pharmacology studies to determine drug tolerance, metabolism and interactions, to determine pharmacokinetics and pharmacodynamics in a small group of people (<30)

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4
Q

What are phase I studies used to determine?

A

Efficacy and safety of a drug (e.g. determine a safe dosage range and identify side effects)

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5
Q

Describe participants in phase I studies

A

Generally healthy volunteers (usually <30)

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6
Q

What are phase II studies?

A

Tests for treatment effect (e.g. test the effect of various doses, usually using biomarkers to measure treatment effect) usually in a larger group of people (30 to 100)

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7
Q

Describe participants in phase II studies

A

Carefully selected, usually with narrow inclusion criteria (usually 30 to 100 participants)

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8
Q

What clinical trial phase is best correlated with traditional “randomized controlled trials”

A

Phase III

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9
Q

Which phase is “the most rigorous clinical investigation of a new treatment”

A

Phase III

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10
Q

What are phase III studies?

A

Studies to determine efficacy of the pharmaceutical or behavioral intervention in large groups of people (several hundred to several thousand) by comparing the intervention to other standard or experimental interventions.

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11
Q

What are phase IV studies?

A

Post-marketing surveillance (studies on the drug after it has been marketed to the general population). They are designed to monitor the effectiveness of the approved intervention in the general population and to collect information about any adverse effects associated with widespread use.

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12
Q

Describe the difference between efficacy and effectiveness

A

Efficacy refers to the ability of an intervention to produce beneficial results under ideal circumstances, whereas effectiveness refers to the ability of an intervention to produce intended results under “routine circumstances” for a specific population

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13
Q

Are Explanatory trials efficacy or effectiveness trials?

A

Efficacy

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14
Q

Are Practical/Pragmatic trials efficacy or effectiveness trials?

A

Effectiveness

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15
Q

What type of trial is the “gold standard” for clinical research?

A

Clinical trial

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16
Q

What type of trial can provide information about the cost-effectiveness of an intervention?

A

Effectiveness trial

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17
Q

Name 4 problems with historical controls

A

Patient selection; measurement (old data issues); co-treatment or patient care improving over time; historical controls tend to exaggerate the value of new treatment

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18
Q

List 3 problems with non-randomized controlled trials

A

Systematic assignment (by DOB, date of presentation, etc.); judgement assignment (both forms of allocation bias); control and intervention groups thusly not comparable

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19
Q

What are the 2 components of formulating a research question?

A

Scholarship and experience

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20
Q

What is the PICO format for research questions?

A

A way to structure research questions around: Population, Intervention (or Exposure), Comparison group and Outcome

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21
Q

What is the FINER criteria?

A

Criteria for good research questions: Feasible (with respect to money, participants, etc.), Interesting, Novel, Ethical, Relevant

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22
Q

Describe the difference between Primary and Secondary Research questions

A

Primary questions form the basis of the hypothesis, should be able to be answered by the study, and need to be addressed in the results. Secondary research questions are related to the primary questions but can be addressed by the same data or different data.

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23
Q

What are the 2 types of Secondary Questions?

A

Subgroup hypotheses and Secondary outcomes

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24
Q

Describe “Secondary outcome” Secondary questions

A

Response variables are different from those addressed by the primary question

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25
Q

Describe the purpose of secondary questions

A

Only to shed light or invite new hypotheses, and not to provide conclusive answers (d/t methodological issues stemming from multiple comparison).

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26
Q

Define Subgroup hypotheses

A

The outcome is compared amongst a subset of participants in the intervention group with participants in the control group

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27
Q

What is the most useful reason for considering subgroups?

A

Examine consistency of results across predefined subgroups

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28
Q

What are 3 requirements of subgroup hypotheses?

A

Must precede data collection, must be limited in number, must be based on reasonable expectations

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29
Q

Define ancillary questions

A

Questions that are not primary or secondary but can be answered (after the fact) by clinical trials because of their infrastructure, interventions and access to participants and data

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30
Q

Define superiority trial. What test is used?

A

Trial designed to show that one treatment is better than other (usual care or placebo, for example); two-sided significance test

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31
Q

Define equivalence trial. What test is used?

A

Trial designed to show that a new treatment is equivalent to a current treatment (equivalence = clinically acceptable difference); two-sided significance test

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32
Q

Define non-inferiority trial. What test is used?

A

Trial designed to show that a new treatment is not worse than a standard treatment by pre-specified “margin of indifference”; one-sided significance test

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33
Q

What typifies a composite outcome?

A

Two or more kinds of events, should be related through a common underlying condition or responding to the same presumed mechanism of action

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34
Q

When is a combination response variable used instead of a single response variable?

A

Combining events to make up a response variable might be useful if any one event occurs too infrequently for the investigator reasonably to expect a significant difference without using a large number of participants

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35
Q

What criteria exist for good Response variables (3)?

A

Must be able to be ascertained completely; must be able to be measured the same way for all participants; assessment should be unbiased and done by people who are not involved in participant follow-up and blinded to the identity of the study group of each participant

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36
Q

Advantages of randomization (3)

A

Removes potential for bias; Groups tend to be comparable with regards to measured or unmeasured confounding factors; Enusring validity of statistical significance tests

37
Q

Define historical control studies

A

In historical control studies, a new intervention is used in a series of patients, and the results are compared to the outcome in a previous series of comparable patients

38
Q

Strengths of using historical control (2)

A

All participants receive intervention; time and costs approximately cut in half; useful if prognosis is poor and/or diagnosis is well-established

39
Q

Limitations of historical control studies

A

Historical control studies are nonrandomized and non-concurrent; shifts in diagnostic criteria; shifts in patient population; changes in patient management; accuracy and completeness of data

40
Q

Describe a [two-period] cross-over design

A

In two period cross-over design, each participant will receive either intervention or control (A or B) in the first period and the alternative in the succeeding period. Allows each participant to serve as their own control.

41
Q

Describe a [two-arm] parallel study

A

Study participants are randomly allocated to either an intervention (treatment) group or control group, with prospective follow-up to assess outcomes

42
Q

What are the advantages of cross-over studies?

A

Increases study power and reduces necessary sample size

43
Q

What are the assumptions of cross-over studies?

A

No carry-over effect of treatments and no “ordering effect of interventions

44
Q

When are cross-over studies impractical?

A

Invasive treatments such as surgical interventions; Illnesses that can be cured by one of the treatments; Clinical events or fatal outcomes; Substantial loss to follow-up

45
Q

Define factorial design

A

Evaluate two interventions compared to control in a single experiment (2x2 grid!)

46
Q

Define incomplete factorial design

A

If it is inappropriate, infeasible, or unethical to address every possible treatment combination, it is possible to leave some of the cells empty

47
Q

Assumptions of equivalence and non-inferiority trials

A

Active control has been shown to be effective vs placebo; studies proving benefits of active control are suitably recent; results showing benefits of active control must be available for comparison; variable used in new study sufficiently sensitive so that any difference between interventions will be detected

48
Q

Describe selection bias

A

Occurs if the allocation process is predictable. In this case, the decision to enter a participant into a trial may be influenced by the anticipated treatment assignment.

49
Q

Describe accidental bias

A

Occurs if the randomization process does not achieve balance with respect to risk factors or prognostic covariates. Usually only a problem for smaller studies.

50
Q

Define fixed allocation randomization

A

Assign the interventions to participants with a prespecified treatment assignment probability, usually equal, and this allocation probability is not altered during study. Includes simple, blocked and stratified randomization.

51
Q

Which type of randomization is synonymous with “complete” randomization

A

Simple randomization

52
Q

Difference between simple and restricted randomization

A

In simple randomization, each assignment is independent of one another and probability of assignment is equal for each assignment. In restricted randomization, some assignments are determined from previous assignments.

53
Q

What is the limitation of simple randomization procedures? What are the consequences of this limitation?

A

Imbalance is the limitation, especially for small sample sizes. Imbalances do not lead to a loss of validity, but they do reduce statistical power.

54
Q

Why is blocked randomization used?

A

To avoid imbalances; at any point during randomization the differences in assignment will be low (never more than k/2), and at some points the assignments will be even between the two groups

55
Q

Limitations of block randomization

A

If block size is known to study staff, then the assignment of last participant in each block is predictable; Data of blocked-assignment studies is more complicated to analyze

56
Q

Define stratified randomization

A

A method that helps achieve comparability between the study groups by stratifying participants for prognostic or risk factors (limit 2-3 variables, more is impractical)

57
Q

Advantages of stratified randomization

A

Comparability; reduces variability, which could improve statistical power if strata are used in analysis

58
Q

Limitations of stratified randomization

A

If different strata have quotas, the increase in necessary participants could delay the study by increasing the recruitment burden; argument that stratification at analysis has same statistical power benefits as stratification at randomization

59
Q

Multicenter trials should always stratify by…

A

Clinic (quality of care varies, one might need to drop out, comparison of results)

60
Q

2 types of adaptive randomization procedures

A

Adapt the allocation probabilities according to imbalances in numbers of participants (biased coin) or in baseline characteristics between the two groups; adjust allocation probabilities according to the responses of participants to the assigned intervention

61
Q

Describe the Adaptive Stratification Method (Minimization)

A

Correcting for imbalances in prognostic factors during randomization by changing assignment probabilities

62
Q

Limitations of adaptive randomization, generally

A

Operationally difficult; requires population stability; data analysis is complicated

63
Q

2 types of response adaptive randomization

A

“Play the winner” (next participant allocated into on the basis of whether or not the last sorted participant experiences successful outcome) and “two-armed bandit” (probability of success created continuously for participants on the basis of success astray are assigned)

64
Q

Disadvantages of response adaptive randomization

A

Imbalance (loss of power); lack of an immediately occurring response variable; significance levels could be biased if population changes; analysis more complicated

65
Q

When should intervention assignment be given, with respect to concealed allocation? What concealed allocation methods are better than others?

A

As close to intervention as possible; telephone/internet > envelope

66
Q

What types of trials have an enhanced ability to show effectiveness of treatments in general population settings?

A

Large, simple trials

67
Q

What considerations exist for determining sample size?

A

Standard statistical parameters (i.e. number of participants necessary to achieve statistical significance); event rate in population/control group; “minimum effect size of interest”; expected loss to follow-up; anticipated treatment adherence/cross-overs

68
Q

What does selecting a higher risk group do for a study?

A

Increases power, reduces generalizability

69
Q

What does selecting a group likely to benefit from the intervention do?

A

Reduces sample size

70
Q

Principal recruitment strategies in clinical settings

A

Medical record review, electronic lab screenings, registries, requests to HCPs

71
Q

Principal recruitment strategies in community settings

A

Mass mailing, screening, advertisement, presentations

72
Q

Define internal validity

A

Whether a study actually measures what it purports to; whether a piece of evidence supports a claim about cause and effect

2 components: Does the treatment appear to improve outcomes, and is the improvement solely due to the treatment (i.e. little to no difference between control and intervention groups)

73
Q

Define external validity

A

Generalizability to the target population

74
Q

Define bias

A

Difference between the true value and that actually obtained due to all causes other than sampling variability

75
Q

Advantages of unblinded trials

A

Less expensive; better reflects clinical practice; investigators more comfortable

76
Q

Disadvantages of unblinded trials

A

Co-treatment bias (concomitant/multiple treatments used by investigator, hard to determine direction or magnitude), ascertainment bias (outcomes misreported), information bias (sx or side effects misreported), withdrawal bias (controls drop out)

77
Q

What type of bias is eliminated by PROBE studies? How? What is one other advantage?

A

Ascertainment; by appointing an independent endpoint/outcome assessment committee; cost-effectiveness

78
Q

Define compensatory treatment bias. What types of studies is this an issue in?

A

Investigators prescribe additional treatment disproportionately to control group; Single-blind and unblinded

79
Q

Define favorable results bias. What types of studies is this an issue in?

A

Investigators or HCPs change management, data collection or reporting of results to favor intervention group or validate hypothesis; Single-blind

80
Q

What types of interventions are common to double-blind trials?

A

Drugs or biologics (surgeries, implantation, lifestyle changes uncommon)

81
Q

What types of bias are avoided by double-blind trials?

A

Selection, co-treatment, concomitant treatment, compensatory treatment, favorable results, ascertainment

82
Q

Disadvantage of triple-blind study

A

Difficult for the committee to monitor participant safety

83
Q

How are efficacy and safety balanced in prevention trials?

A

Low dosages; if effective, it will prevent the condition in a few people

84
Q

What type of control treatment is placebo?

A

Inactive control treatment

85
Q

Define a cross-over, with regards to study participants

A

Intervention to control, or control to intervention

86
Q

Define a drop-in, with regards to study participants

A

ONLY refers to those cross-over who go control to intervention

87
Q

Define a drop-out, with regards to study participants

A

Intervention participant who fails to adhere to regimen

88
Q

Define a withdrawal, with regards to study participants

A

A drop-out who fails to adhere to regimen specifically because they stop following up

89
Q

What is a run-in period? What are the different types?

A

A run-in period precedes randomization and seeks to identify non-adherers so that they may be excluded from randomization and thus the rest of the study; active run-in (participants given medication, monitored for adverse effects) and placebo run-in (participants monitored for withdrawal/drop-out)

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