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KCUMB Epidemiology > Exam 2 Material > Flashcards

Exam 2 Material Flashcards

1
Q

Quantitative study design

A

Design in which the results are quantifiable (involve numbers)

Ex: Interventional and observational studies

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2
Q

Interventional study design

A

“Experimental” study design in which researcher select an intervention (usually an exposure) and forces allocation groups using randomization

Best design to prove causation, therefore is the only design that is FDA-approved

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3
Q

Observational study design

A

“Observation of naturally occurring events”

Study design in which researchers do NOT force allocation groups

Typically does not prove causation

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4
Q

Population vs study population

A

Population is NOT the same as a study population.

Population = all individuals making up a common group

Study population = a portion of the full population that representative of the group (ie. sample)

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5
Q

Null hypothesis (Ho)

A

Perspective stating that there is no true difference between comparison groups

“Innocent until proven guilty”

If not rejected - there is NO difference between groups
If rejected - there IS a difference between the groups

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6
Q

Statistical perspectives/questions of:
Superiority
Non-inferiority
Equivalency

A

Superiority: is the drug superior to ___?
Ho = the drug is NOT superior to ___.

Non-inferiority: is the drug NOT worst than ___?
Ho = the drug IS worst than __.
Comparison is typically to the “golden standard”

Equivalency: is the drug equal in effect to ___?
Ho = the drug is NOT equal to ___.

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7
Q

Alternative hypothesis

A

Perspective that there IS a difference between comparison groups

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8
Q

Type I error

A

False (+)

Null hypothesis has been inaccurately REJECTED

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9
Q

Type II Error

A

False (-)

Null hypothesis has been inaccurately ACCEPTED

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10
Q

Probability sampling

A

Equal opportunity (known, non-zero probability) of selection to be included in a sample

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11
Q

Simple random sampling

A

Completely random sampling

Where each element is assigned a random number and then numbers are randomly selected until desired sample size

Ex. Flipping a coin

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12
Q

Systematic random sampling

A

Where each element is assigned a random number, and then selection of sample is based on a predetermined sampling interval (take an element every Nth element)

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13
Q

Stratified random sampling

A

Split population into strata based on specific characteristic and then do simple random sampling in each strata (where elements are assigned random numbers and random number are selected to make sample)

Ex. Male and female strata

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14
Q

Stratified disproportionate random sampling

A

“Weighing” statrified sample to make sample proportional to population

Useful for over-sampling

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15
Q

Multi-stage random sampling

A

Random selection at different stage intervals

Using simple random sampling at multiple stages toward patient selection

Ex. Regions -> zip codes -> clinic -> patient

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16
Q

Cluster multi-stage random sampling

A

Sampling ALL elements clustered together (at any stage) of multi-stage random sampling scheme

Ex. All clinics in a zip code are included

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17
Q

Quasi-systematic sampling

A

Sampling from a fraction of the population

-may introduce selection bias

Ex. Sampling from all persons with names beginning with “M-Z”

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18
Q

Patient-oriented outcome (POE)

A

An outcome that is more directly important to a patient

Ex. Risk of heart attack (POE) vs high BP (DOE)

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19
Q

Disease-oriented outcome (DOE)

A

Outcome attributable to diseases, but not necessarily of great concern to patients

Ex. High blood pressure (DOE) vs heart attack (POE)

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20
Q

EQUIPOISE

A

Confidence that an intervention is worthwhile (risk vs benefit)in order to be tested/used in humans

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21
Q

4 Principles of Bioethics

A

Autonomy - self-rule; allow an individual to make ones own informed decision with understand of risks/benefits involved and without outside influence

Beneficence - do good for the individual (NOT society); must have the individual’s best interest in mind

Non-maleficence - do no harm to the patient

Justice - treat individuals equally and fairly regardless of any characteristics they may have

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22
Q

Guidelines of the Belmont Report

A
  1. Respect for persons = research is conducted on a volunteer basis
  2. Beneficence = risks of research are justified by potential benefits
  3. Justice = risk and benefits are equally distributed among the study population
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23
Q

Consent

A

Agreement to participate of a mentally-capable, fully informed 18+ yo

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24
Q

Assent

A

Agreement to participate of a minor or individual unable to otherwise give legal consent after guardians have been fully informed of the risks and benefits

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25
Q

Institutional Review Board (IRB)

A

Protects human subjects from undue risks of research

Regulated by Dept. of Human Health Services (DHHS)

Enforced by the Office of Human Research Protections (OHRP)

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26
Q

Full Board vs. Expedited vs. Exempt

A

Full board = for all interventional trials with more than a minimal risk to the human subjects; requires the most time and resources

Expedited = for trials with minimal risk and no/little patient identifiers

Exempt = for trials that have no/little risk and no patient identifiers, or use existing data; required the least time and resources

*all are for BEFORE the study begins

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27
Q

Data Safety and Monitoring Board (DSMB)

A

Board that reviews a study and provides interim analysis as the study progresses

Can stop research if findings are overly positive or overly-negative

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28
Q

Pre-clinical (interventional study)

A

Bench/animal research prior to human investigation

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29
Q

Phase 0 (interventional studies)

A

First in-human use

  1. Assesses drug’s target actions
  2. Used on healthy or diseased volunteers
  3. Small sample (<20)
  4. Short duration (single dose - few days)
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30
Q

Phase 1 (interventional study)

A
  1. Assesses safety/tolerance of pharmacokinetics
  2. Used on healthy or diseased volunteers
  3. Small sample (20-80)
  4. Short duration (few wks)
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31
Q

Phase 2 (interventional study)

A
  1. Assesses effectiveness (and safety); an expansion off phase 1
  2. Used on DISEASED volunteers
  3. Larger sample (100-300)
  4. Longer duration (few wks-months)
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32
Q

Phase 3 (interventional study)

A
  1. Assesses safety/effectiveness over longer period before FDA approval
  2. Used on DISEASED volunteers (may expand inclusion criteria)
  3. Large sample (hundreds-thousands)
  4. Long duration (months-years)
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33
Q

Phase 4 (interventional study)

A
  1. Post-marketing studies assessing long-term safety/effectiveness post FDA approval
  2. Used on DISEASED volunteers
  3. Huge sample (thousands-hundred thousands)
  4. Long duration (years-ongoing)
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34
Q

Pros/Cons of Interventional studies

A

Pro:

  • can demonstration causation
  • only study that can lead to FDA approval

Con:

  • expensive / complicated / takes time
  • ethical considerations (balancing risk with benefit in human trials)
  • must ensure external validity can be upheld
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35
Q

Exploratory studies

A

Research study that seeks to precisely answer research questions by “exploring” the safety/usefulness/efficiency of an intervention within a non-real clinical setting

36
Q

Explanatory studies

A

Research study that seeks to “explain” how to treat a disease in relation to a patient in a real-life clinical setting

Is less restrictive and more applicable to patients than exploratory studies

37
Q

Simple study design

A

An interventional study design in which subjects are divided in 1 step of randomization

Useful for testing a single hypothesis

38
Q

Factorial study design

A

An interventional study design in which subjects are divided with 2+ steps of randomization using subdivisions

Useful for looking at multiple factors and their interactions; can test multiple hypotheses at the same time based on different subdivision combinations

Note: if too complex, the study may restrict generalizability

39
Q

Parallel study design

A

An interventional study design in which there is NO SWITCHING of intervention groups after initial randomaization

40
Q

Cross-over study design

A

An interventional study design in which subjects may serve as their own control by crossing between intervention groups during wash-out phases

Pro:
Allows for “between”/“within” group comparisons and smaller sample size (since data can be collected from the same person)

Con:
Only for long-term conditions/diseases
Subjects are studies for longer duration (enough to collect data twice)
Beware of carry-over effects (wash-out must be done correctly)
Complex data analysis
Internal validity may be compromised (treatment may affect subjects differently at different times)

41
Q

What is the use of a run-in/lead-in phase?

A

Acts as a wash-out phase prior to the study beginning

Allows for researchers to determine a baseline for the subjects (removes existing medication in their system and can assess their protocol compliance)

42
Q

Patient oriented endpoints (POE)

A

Results that are more clinically relevant or important to the patient

Ex: heart attack, stroke, etc.

43
Q

Disease oriented endpoint (DOE)

A

Study result that evaluates the risk of a patient oriented endpoint

Ex: blood pressure, cholesterol level, etc.

44
Q

Randomization (3 types)

A

Randomization = selection of subjects such that study groups are made as equal as possible

  1. Simple randomization - equal probability of allocation into either study group
  2. Blocked randomization - randomization that ensures balance within each intervention group
  3. Stratified randomization - randomization that balances groups based on known confounding variables
45
Q

Single blind masking

A

Only subjects do not known what interventional group they are in

46
Q

Double blind masking

A

Both researchers and subjects do not know which intervention groups the subjects are in

47
Q

Open-label masking

A

Unmasked/unblinded studies

48
Q

Placebo effect

A

Improvement in condition by power of suggestion

49
Q

What can assess adequacy of blinding?

A

Post hoc survey’s

50
Q

Placebo (“dummy”) treatment

A

An inert treatment that is made to look identical in ALL aspects to the active treatment

51
Q

Hawthorne effect

A

When study subjects change behavior solely because they know they are being studied

52
Q

Intention-to-treat

A

The most conservative form of managing drop-outs/loss-to-follow-up

Data from the drop-out is included in the study anayway

Pros:

  • preserves randomization
  • preserves base-line characteristics including balance for cofounders
  • maintains statistical power by keeping the original sample size
53
Q

Per protocol (aka. Efficiency analysis)

A

Form of drop-out/loss-to-follow-up management in which they are ignored

Their data is removed from the study

Con:

  • prone to type II error
  • reduces generalizability
54
Q

As treated

A

Form of managing drop-out/loss-to-follow-up in which end results are somewhat estimated

Data from the missing subjects is used as if they had stayed in the study

55
Q

Assessing adherence

A

“Are subjects following protocol?”

Ex. Test drug levels / count pills / check bottle counter tops

56
Q

Improving adherence

A

“How can we ensure subjects follow protocol?”

Ex. Increase follow-up visits/communication; treatment alarms; dosage containers or medication blisters for easy access

57
Q

Case control studies are particularly impacted by what kind of bias?

A

Selection Bias and Recall Bias

58
Q

Sampling for Nested Case-Control studies:

A

Survivor sampling = samples from non-diseased individuals at the end of a previous prospective study

Base sampling = samples from non-diseased individuals from the beginning of a previous prospective study

Risk-set sampling = sampling from non-diseased individuals from within the prospective study period at the same time when case was diagnosed (control group is time dependent)

59
Q

Case Control Studies

A

Observational studies in which group assignments are based on disease status; retrospective study

Strengths:

  • useful for studying rare diseases
  • can assess multiple exposures on one disease
  • useful for when disease has a long induction/latent period

Weaknesses:

  • cannot demonstrate causation
  • impacted by selection and recall bias
  • selection of controls is difficult (selection is irrespective of exposure)
60
Q

Individual matching

A

Matching individuals based on patient-based characteristics to control for confounder

Ex. Groups will have same number of males and females

61
Q

Group matching

A

Matching proportions of characteristics between case and control groups

Ex. 41% of cases are white and 41% of controls are white

62
Q

Cohort studies

A

An observational study in which group assignment is based on exposure status or a shared common factor; can be conducted prospectively, retrospectively, or am-bidirectionally

Strengths:

  • useful for studying rare exposures
  • can represent Temporality (if conducted prospectively)
  • can assess multiple outcomes/diseases from 1 exposure

Weakness:

  • cannot demonstrate causation
  • exposures may change over time (are hard to control)
  • long induction/latency is not good for Prospective Cohorts
63
Q

What biases typically impact Cohort Studies?

A

Healthy-worker effect and Selection Bias

64
Q

Internal validity

A

The extent to which a study’s results accurately reflect what was being assessed

65
Q

External validity

A

The extent to which a study’s results are applicable to an entire population; generalizability

66
Q

Validity

A

The ability to discern between those that have disease and those that do NOT have disease

67
Q

What can be “chosen” to minimize false positives and/or false negatives?

A

Cut-offs

68
Q

Reliability

A

The ability of a test to give consistent results

69
Q

LR+ and LR-

A

LR+ : the likelihood of a diseased individual receiving a (+) result compared to a non-diseased individual; useful if LR+>10
=sensitivity/(1-specificity)

LR- : the likelihood of a diseased individual receiving a. (-) result compared to a non-diseased individual; useful if LR-<0.1
=(1-sensitivity)/specificity

70
Q

Likelihood Ratios

A

Ratio of the probability of receiving a test result (+/-) in the diseased group compared to the non-diseased group

71
Q

Loss-to-follow-up increases what type of error?

A

Type II Error

72
Q

Birth cohort vs. Inception cohort vs. Exposure cohort

A

Birth cohort - groups are based on time period and region of birth

Inception cohort - groups are based on a common factor

Exposure cohort - groups are based on common exposure; ex. One time events

73
Q

Fixed cohort

A

Cohort in which sample cannot be added to (fixed max from starting sample), but can have loss-to-follow-up

74
Q

Closed cohort

A

Cohort in which sample cannot be added to or reduced (fixed at both ends)

75
Q

Open/dynamic cohort

A

Cohort in which sample can be added to and/or reduced

76
Q

Cross-sectional study

A

An observational study that captures information about an exposure and disease at the same time; aka. Prevalence study

Typically are large-scale, national surveys

Strengths:

  • quick / easy / relatively cheap
  • estimates prevalence rates
  • can use the same data for different research questions

Weaknesses:

  • difficulty in studying rare diseases
  • cannot determine temporal relationship for cause/effect
77
Q

What cross-sectional survey combines interviews with physical exams?

A

National Health and Nutrition Examination Survey (NHANES)

78
Q

How does the National Ambulatory Medical Care Survey sample a population?

A

Multi-step random sampling

79
Q

What cross-sectional survey collected data with an interview by telephone?

A

BRFSS - Behavioral Risk Factor Surveillance System

80
Q

2 questions patients should ask their physician before a medical screening:

A
  1. How accurate is the test?

2. How confident are you that the test is accurate in its prediction?

81
Q

Sensitivity

A

How accurate a test is in detecting disease in someone who actually has the disease; proportion of true positives

=TP/(#diseased people)
=TP/(TP+FN)

82
Q

Specificity

A

How accurate a test is in detecting the absence of disease in a non-diseased individual; proportion of true negatives

=TN/(#non-diseased)
=TN/(TN+FP)

83
Q

Positive Predictive Value (PPV)

A

How accurate a (+) test predicts the presence of disease

=TP/(all positive results)
=TP/(TP+FP)

84
Q

Negative Predictive Value (NPV)

A

How accurate a (-) result is in predicting the absence of disease

=TN/(all negative results)
=TN/(TN+FN)

85
Q

What is the effect of prevalence on PPV and NPV?

A

Increasing prevalence causes an increase in PPV and NPV

This is because the more frequent a disease is in a community, the easier it is to “find” the disease

86
Q

Diagnostic Accuracy

A

Proportion of screening in a sample that are correctly identifying the presence of absence of disease

=(TP+TN)/(total sample)
=(TP+TN)/(TP+TN+FP+FN)

KCUMB Epidemiology (3 decks)

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