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Healthy Pop Exam 1 > Epidemiology > Flashcards

Epidemiology Flashcards

1
Q

Epidemiology:

A

The study of distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems

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2
Q

Descriptive Studies:

A

Describe the ocurrence and distribution of one or more variables in a population, group, or sample
Ex: Rabies by species

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3
Q

Analytical Studies:

A

Measure the relationship or association between two variables, usually a risk factor (or exposure) and an outcome
Ex: Rabies positivity rate in cats/dogs

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4
Q

Questions asked by descriptive studies:

A

Who gets sick and who doesn’t?
Where?
When?
How are cases connected?
How big is the problem?

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5
Q

Questions asked by analytical studies:

A

Why did this occur?
What can we do?

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6
Q

Determinants:

A

Host
Agent
Environments

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7
Q

Types of population data:

A

Measurement (quantitative)
Count (Categorical/Qualitative)

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8
Q

Examples of measurement data:

A

Weight, Hematocrit, BUN, Age, Survival Time, Titer, etc

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9
Q

Count data examples:

A

Breed, Sex, +/-, Old/Young, Healthy/Sick/Dead

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10
Q

Incidence answers what question?

A

What is the rate of occurrence of new cases?

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11
Q

Prevalence answers which question?

A

What proportion of animals are sick at once

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12
Q

Prevalence Calculation:

A

All Current Cases/Population at Risk

At a point in time

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13
Q

Incidence calculation :

A

NEW cases/Population at Risk

During a specific time interval

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14
Q

Primary Prevention:

A

An action that PREVENTS disease in healthy animals

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15
Q

Secondary prevention:

A

Identifying animals with disease to prevent symptoms

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16
Q

Tertiary Prevention:

A

Prevention of complications in animals who have the disease

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17
Q

P-Value:

A

Probability that a difference of this size or large would be observed it there really was no difference between groups (probability of this happening randomly)

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18
Q

Significant P-Values:

A

<0.05

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19
Q

What answers the question “could the difference we found between the means be just due to chance variation?”

A

P-value

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20
Q

What answers the question “how certain are we of the size of the difference between the means?”

A

Confidence Interval

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21
Q

What answers the question “what is the rate of occurrence of new cases?”

A

Incidence

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22
Q

Case Fatality Calculation

A

Death among cases/total cases

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23
Q

What answers the question “What proportion of animals are sick at once?”

A

Prevalence

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24
Q

What answers “what proportion of cases die?”

A

Case Fatality Rate

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25
Q

Risk Ratio/Relative Risk:

A

Incidence w/ risk factor/incidence w/o risk factor

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26
Q

Risk Difference/Attributable Risk:

A

Incidence w/ risk factor - incidence w/o risk factor

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27
Q

Attributable Fraction:

A

Risk Difference/Incidence in HIGH risk group

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28
Q

Prevalence Ratio:

A

Prevalence w/ risk factor/ Prevalence w/o risk factor

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29
Q

Prevalence Difference:

A

Prevalence w/ risk factor - Prevalence w/o risk factor

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30
Q

Odds Ratio:

A

Odds of disease w/ risk factor/ Odds w/o risk factor

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31
Q

What answers the question “how big is the difference between the individuals with and without a particular risk factor?” for QUANTITATIVE studies?

A

Differences in means

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32
Q

What answers the question “how big is the difference between the individuals with and without a particular risk factor?” for QUALITATIVE studies?

A

Relative Risk, Prevalence Ratio, Odds Ratio, Risk Difference, Prevalence Difference, Att Fraction in the Exposed

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33
Q

Three general categories of studies:

A

Descriptive, Observational, Experimental

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34
Q

Two types of analytical studies:

A

Observational and Experimental

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35
Q

In a cohort study, you know the __________ and you are working to observe the ___________.

A

Exposure; Outcome

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36
Q

In a case-control study, you know the __________ and you are working to observe the ___________.

A

outcome; exposure

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37
Q

Three types of observational studies:

A

Cross-sectional
Case-control
Cohort

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38
Q

Cross-sectional studies identifies ______________, not _____________.

A

Association; Causation

39
Q

Study that analyzes data across a population at a single point of time.

A

Cross-sectional

40
Q

Characteristic of sampling for cross-sectional studies:

A

representative of population, not related to outcome/exposure

41
Q

Disease measures in cross-sectional studies:

A

Prevalence ratio & difference
Attributable fraction of the exposed
Prevalence Odds Ratio

42
Q

Limitations of cross-sectional studies:

A

-Least useful for establishing causal relationships
-Prevalence reflects incidence & duration (can underestimate risk)
-Impractical for rare diseases
-Poor sampling=> unusable results

43
Q

What type of study looks at outcomes (cases) and works backwards to find exposures?

A

Case-control

44
Q

Characteristic of sampling for case-control studies:

A

Based on outcome of interest (cases & controls)

45
Q

What cannot be calculated for case-control studies?

A

Incidence, Prevalence, Population Risk, Attributable Risk

46
Q

What calculation can you assess with case-control studies:

A

Odds ratio

47
Q

Limitations for case-control studies:

A

-Problems w/ temporal sequence
-Values we cant calculate
-Can’t assess rare exposures
-Appropriate control group is hard to pick
-High potential for bias

48
Q

Best study design for rare diseases:

A

Case-Control

49
Q

Prospective cohort study timing:

A

Selects cohort at start of study and follows

50
Q

Retrospective cohort study timing:

A

Comparing incidence of disease in exposed v unexposed that has already occurred

51
Q

What is the only thing that should differ between groups in clinical trials?

A

Treatment

52
Q

Types of allocation for clinical trials:

A

Random or Non-Random

53
Q

Options for random allocation:

A

Completely random
Random
By Pairs
Within Blocks

54
Q

Options for non-random bias:

A

Systematic
Historical non-random allocation
Clinician’s discretion

55
Q

Specificity:

A

True negatives/(true negatives + false positives)

56
Q

Sensitivity:

A

True Positives/(True Positives + False Negatives)

57
Q

Positive Predictive Value:

A

True Positives/(True Positives+False Positives)

58
Q

Negative Predictive Value:

A

True Negatives/(True Positives + False Positives)

59
Q

Low Prevalence ____________ NPV and _____________ PPV

A

Increases; Decreases

60
Q

High Prevalence ____________ NPV and _____________ PPV

A

decreases; increases

61
Q

When is testing in parallel helpful:

A

Looking for two different markers (Ie testing for antigen in early dz and antibody in late dz)

62
Q

Testing in series increases _________ and decreases ____________.

A

Specificity; Sensitivity

63
Q

Parallel Testing increases ____________ and decreases _____________

A

Sensitivity; Specificity

64
Q

EID:

A

Emerging infectious disease
One that has appeared in a population for the first time or that may have existed previously but is rapidly increasing in incidence or geographic range

65
Q

Three questions you should ask in an epidemiologic investigation?

A

Where did the disease come from?
What management factors allowed it to spread?
Where did it go from here?

66
Q

Which cases should be reported?

A

All diagnosed/suspected cases of diseases with an APHIS control or eradication program
All diagnosed/suspected cases of FADs

67
Q

General Management of a disease outbreak:

A

Get diagnosis
Determine and control the source
stop transmission
Eliminate the disease

68
Q

Internal validity excludes the effects of:

A

Bias
Confounding
Random Error

69
Q

Internal validity:

A

Does the results represent the truth in the population we are studying

70
Q

External validity:

A

Can the findings be generalized to other contexts

71
Q

The relationship between internal & external validity:

A

If the study lacks internal validity, then external validity is irrelevant

72
Q

Random error vs. Systematic error:

A

RE is error due to chance
SE error due to recognizable source
Both can exist at the same time

73
Q

Effect of bias:

A

Leads to the appearance of an association when there is none, or obscures an association that really exists

74
Q

Selection Bias:

A

Affects WHO is in the 2x2 table

75
Q

Information Bias:

A

Where in the 2x2 are people put

76
Q

Bias towards the null:

A

observed value is closer to 1 (or 0 in the case of difference measurements) than is the true value

77
Q

Bias away from the null:

A

observed value is farther from 1 (or 0 in the case of difference measurements) than is the true value

78
Q

If the truth is RR=1.9 and the biased result is RR=1.4, which direction is it biased and is the association over or underestimated?

A

Bias towards the null
True association is underestimated

79
Q

If the truth is RR=0.4 and the biased is RR=0.7, which direction is it biased and is the association over or underestimated?

A

Bias towards the null
True association is underestimated

80
Q

If the truth is RR=2.0 and the biased is RR=2.6, which direction is it biased and is the association over or underestimated?

A

Bias towards the null
True association is underestimated

81
Q

If the truth is RR=0.5 and the biased is RR=0.3, which direction is it biased and is the association over or underestimated?

A

Bias towards the null
True association is underestimated

82
Q

Selection bias is most likely in what type of study?

A

Case-control

83
Q

How does selection bias occur in case control studies? (2)

A

Control Selection
Differential Participation

84
Q

Prevention of Control Selection:

A

Use identical selection criteria for cases and controls

85
Q

Prevention of differential participation:

A

obtain high participation rates for all groups

86
Q

How does selection bias occur in cohort studies? (2)

A

Differential Participation
Differential Loss to Follow-up

87
Q

How to prevent selection bias in cohort studies?

A

Obtain (dif. participation) and maintain (dif. loss) high participation rates in all groups

88
Q

Two components of misclassification bias:

A

How accurately can you measure exposures?
How accurately can you measure disease?

89
Q

Examples of non-differential misclassification bias:

A

Recall bias
Interviewer Bias

90
Q

What is the most common type of bias?

A

Measurement/Misclassification Error

91
Q

Effects of non-differential measurement error:

A

Bias towards the null

92
Q

Effects of differential measurement error:

A

Bias in either direction

93
Q

Difference between Differential and non-differential misclassification:

A

Non-differential (random) has roughly equal errors between groups (masks any true difference)
Differential (non-random) has better information in one group which causes over or under estimation of association

94
Q
A

Healthy Pop Exam 1 (4 decks)

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