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*CPH Exam 2021 > Epidemiology > Flashcards

Epidemiology Flashcards

1
Q

surveillance

A

ongoing, systematic collection, analysis, and interpretation of health-related data

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2
Q

goal of surveillance

A

to provide information to be used for public health action

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3
Q

Must the CDC be invited by a state before conducting public health surveillance?

A

Yes

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4
Q

Passive surveillance

A
  • diseases are reported by health care providers
  • simple and inexpensive
  • limited by incompleteness of reporting and variability of quality
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5
Q

active surveillance

A
  • health agencies contact health providers seeking reports
  • ensures more complete reporting of conditions
  • time consuming and expensive
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6
Q

sentinel surveillance

A

reporting of health events by health professionals who are selected to represent a geographic area or a specific reporting group

can be active or passive

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7
Q

syndromic surveillance

A

focuses on one or more symptoms rather than a physician-diagnosed or laboratory confirmed disease

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8
Q

Epidemiology

A

the study of the distribution and determinants of health-related states or events in specified populations;

  • study (scientific, systematic, data-driven)
  • distribution (frequency/pattern)
  • determinants (causes, risk factors)
  • populations (neighborhoods, school, city, state, country, state)
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9
Q

Disease Distribution

A

analysis of patterns

describes who gets the disease, where people with the disease are located, and how these aspects of disease change over time

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10
Q

endemic

A

the ongoing, usual level of, or constant presence of a MMD within a given population

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11
Q

epidemic

A

outbreak or occurrence of a MMD clearly in excess of usual level of expectancy in a defined community or region

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12
Q

pandemic

A

worldwide epidemic

Ex: HIV; COVID-19

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13
Q

descriptive epidemiology

A

Answers - Who is getting the disease?

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14
Q

fixed population

A

permanent membership based on an event

ex: Hiroshima survivors

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15
Q

Transient/dynamic population

A

membership based on a condition that changes

ex: where you live

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16
Q

counts

A

of cases

  • answers “How many?”
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17
Q

ratio

A

one number (x) / another number (y)

  • can be related or independent
  • range 0 to infinity
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18
Q

proportion

A

type of ratio; expressed as a percentage

numerator is subset of the denominator;
x/(x+y)

range 0 to 1

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19
Q

risk

A

probability of outcome occurring among at risk population during a time period

a/N
a=# of new onset cases
N = population-at-risk at beginning of follow-up

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20
Q

rate

A

quantity per unit of time; measures speed at which things happen

range: zero to infinity
ex: heart rate - 60 beats per minute

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21
Q

incidence rate/density

A

of new cases (incidence) / # of person-time (PT) of observation

ex: 1 case/4.5 person-years

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22
Q

person-time assumption

A

assumes rate is constant over different periods of time

ex: 100 persons followed for 10 years = 1000 person years
ex: 1000 persons followed for 1 year = 1000 person years

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23
Q

prevalence

A

proportion;

of existing cases of MMD / # of total population

range 0 to 1

“snapshot”

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24
Q

case fatality rate

A

not a rate, is a proportion

of deaths from an illness/# of people with the illness

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25
Q

proportionate mortality

A

the proportion of deaths caused by a specific disease / all deaths

used to determine leading causes of mortality

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26
Q

crude mortality rate

A

of deaths from all causes / total population in a given time period

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27
Q

cause-specific mortality rate

A

deaths from a specific cause / total population in a given time period

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28
Q

age-specific mortality rate

A

of deaths from all causes in a specific age group / # population in specific age group in a given time period

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29
Q

control for confounding by:

A
  1. stratification

2. direct standardization

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30
Q

Experimental Study Designs

A
  1. RCT

2. Clinical trial

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31
Q

Observational Study Designs

A
  1. Case reports/series
  2. Ecological
  3. Cross-Sectional
  4. Cohort
  5. Case-Control
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32
Q

RCT

A

compares exposure and outcome among different groups

exposure is randomly assigned by researcher

customary to present patient characteristics table

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33
Q

RCT process

A
  1. Identify study population
  2. randomly assign into 2+ exposure groups
  3. categorize into outcome groups (e.g. cured/not cured)
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34
Q

Clinical trial limitations

A
  1. ethical considerations
  2. select population (may not be generalized)
  3. duration (expensive, time consuming)
  4. adherence (ensuring subjects comply with study procedure)
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35
Q

placebo

A

ensures control and treatment group have the same “experience”

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36
Q

single blinding

A

subjects unaware of assigned exposure

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37
Q

double blinding

A

both subjects and researchers do not know assigned exposure

standard

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38
Q

infant mortality rate

A

of deaths of infants less than 1 year of age / # of infants less than 1 year of age within a given time period

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39
Q

MMD

A

Mortality, Morbidity, Disability

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40
Q

incidence

A

of new cases of disease

41
Q

disease frequency

A

how often does the MMD occur in the population?

42
Q

cumulative incidence (CI)

A

of new cases of disease / # in at risk population over a specified period of time

estimates the probability that a person will develop disease during a specified time

43
Q

Cumulative Incidence is used mainly for _____ populations

A

fixed

44
Q

incidence decreases + people are living longer with the disease =

A

increased prevalence

45
Q

incidence increases + duration is short =

A

decreased prevalence

46
Q

incidence decreases + duration is short =

A

decreased prevalence

47
Q

relative risk

A

ratio

rate in exposed/rate in unexposed

48
Q

relative risk 2x2 table

A

(a/a+b)/(c/c+d)

49
Q

odds ratio

A

the odds that an outcome will occur given a particular exposure; compared to the odds of the outcome occurring in the absence of that exposure

50
Q

odds ratios are most commonly used in _____, but can also be used in _____ and _____.

A

case-control studies

cross-sectional and cohort

51
Q

odds ratio 2x2

A

(a/b)/(c/d)

-or-

ad/bc

52
Q

RR is approximate to the OR when:

A

the disease is rare

53
Q

ecological studies: unit of analysis

A

population or groups

54
Q

ecological studies: exposure status

A

based on the population

55
Q

ecological fallacy

A

making assumptions about the individual based on findings at the population level

56
Q

ecological studies: time

A

varies

57
Q

cross-sectional: time

A

snap-shot

58
Q

cross-sectional: population

A

individual level;

selected without regard to exposure or disease status

59
Q

cross-sectional: measure

A

prevalence

60
Q

cross-sectional: Measure of association

A

odds ratio

cannot determine cause and effect

61
Q

case control study

A
  • disease is rare
  • disease has a long induction and latent period
  • little is known about the disease
62
Q

case control study: selection of cases based on _____.

A

outcome

63
Q

cohort study

A
  • 2+ groups begin disease free
  • selection based on exposure
  • followed for outcome
  • observational equivalent of experimental studies, but unable to allocate exposure
64
Q

cohort study purpose

A

studies causes, preventions, and treatments for diseases

65
Q

randomized control trials

A

investigate the role of some “agent” in the prevention or treatment of disease

researcher allocates agent

gold standard

66
Q

goal of randomization

A

to achieve baseline comparability between compared groups on factors relating to outcome

provides balances with respect to known and unknown factors

67
Q

The _____ the groups, the _____ randomization works.

A

larger, better

68
Q

strategies for increasing compliance?

A

design

throughout the study

69
Q

purpose of blinding

A

to avoid bias in ascertainment of outcome

70
Q

internal validity

A

the degree to which
the results are attributable to the
independent variable and not some
other rival explanation

71
Q

external validity

A

the extent to which
the results of a study can be
generalized

72
Q

threats to validity

A

bias, chance, confounding

73
Q

chance

A

random variation

74
Q

as we _____ the sample size, the impact of chance _____.

A

increase; decreases

75
Q

bias

A

systematic error in the design or conduct of a study;
unintended mistake of the researcher

not affected by sample size

best to control for at the design stage

76
Q

confounding

A

not a mistake, but needs to be controlled for

not impacted by sample size

can be controlled for at the design and/or analysis stage

77
Q

selection bias

A

systematic error in the method of selecting study participants

78
Q

misclassification bias

A

systematic error in the procedures for gathering exposure/disease information

79
Q

bias leads to:

A

wrong results leading to misleading conclusions

80
Q

Dealing with bias at design stage

A
  1. subject selection

2. subject/study personnel blinded to subject status

81
Q

Dealing with bias at data collection

A
  • definitions
  • measurements
  • standardization
  • quality control
82
Q

confounding

A

distortion in the measures of the association between exposure and outcome

83
Q

mixing of effects

A

association between exposure and disease is distorted

mixed with the effect of another associated factor

84
Q

Confounding arises when important _____ factors are _____ distributed across groups being compared.

A

extraneous; differentially

85
Q

screening

A

classifies individuals with respect to their likelihood of having a particular disease

86
Q

potential harms of screening

A
  • false positive
  • unnecessary interventions and anxiety
  • over-diagnosis
  • cost
  • discomfort
  • embarrassment
87
Q

WHO recommendations for screenings

A
  • important health problem (prevalence/severity)
  • treatment should be available
  • available facilities for diagnosis and treatment
  • latent stage of disease
  • available test for the disease
88
Q

prevalence

A

(TP + FN) / total

89
Q

sensitivity

A

TP / (TP + FN)

90
Q

specificity

A

TN / (TN + FP)

91
Q

PPV

A

TP / (TP + FP)

92
Q

NPV

A

TN / (TN + FN)

93
Q

Lowering criterion of positivity results in _____ sensitivity and _____ specificity

A

increased; decreased

94
Q

Increasing criterion of positivity _____ sensitivity and _____ specificity.

A

decreased; increased

95
Q

for continuous data, the decision for the screening cut point involves weighing the consequences of _____ against _____.

A

false negatives; false positives

96
Q

Sensitivity should be increased when _____.

A

the penalty associated with missing a case is high

ex: very infectious disease
ex: when subsequent diagnostic evals have minimal risk or cost

97
Q

specificity should be increased when _____.

A

the costs or risks associated with further diagnostics are substantial.

ex: invasive diagnostics (biopsies)

98
Q

preclinical phase (Natural progression of disease)

A

period between developing the disease and symptom onset

99
Q

clinical phase (Natural progression of disease)

A

diagnosis, seek care, treatment, outcome

*CPH Exam 2021 (10 decks)

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