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USPS Midterm 1 > EPI > Flashcards

EPI Flashcards

1
Q

Epidemiology purpose

A

Quantify disease/death in pop
Quantify causes of disease in pop
Identify causal links to disease and death
Test claims of interventions efficiency
Break causal links

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2
Q

Classical Epidemiological Practice Steps

A
  1. Identify a health problem
  2. Describe its distribution (descriptive epi)
  3. Hypothesize potential causes
  4. Determine causal associations (analytical epi)
  5. Intervene
  6. Assess for results
  7. Repeat
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3
Q

Descriptive Epi purpose

A

describing distribution of disease in pop/ health conditions and determinants

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4
Q

Variables used in descriptive epi

A

time, person, place, measures of morbidity (and why we are using these). use to analyze outcomes AND determinants

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5
Q

We have to see if associations are…

A

causal

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6
Q

An observed association can be due to 4 things:

A
  1. cause
  2. chance
  3. confounding
  4. bias
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7
Q

Intervention can help with all 3 levels of prevention

A
  1. Primary: Prevent initial development
  2. Screen and catch early to reduce severity
  3. Reduce clinically apparent disease’s ultimate impact through treatment or rehabilitation
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8
Q

Goals of Descriptive Epi

A

Understand burden of disease in population
Understand causal links to disease, death, and disability
Generate hypotheses for further study
Track trends in pop. health

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9
Q

Morbidity

A

Disease and disability

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10
Q

Mortality

A

Death

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11
Q

Counts

A

of cases in a pop

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12
Q

Fractions

A

Proportion of population that is a case

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13
Q

Rate

A

Cases per time (fraction per time)

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14
Q

In descriptive epi, analyse outcomes and determinants by these 3 things

A

time, person, place

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15
Q

“Place”

A

urban/rural, community, political

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16
Q

“Person”

A

education status, wealth status, race, gender/sex, disability

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17
Q

Incidence

A

of new cases in a defined pop

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18
Q

Prevalence

A

Current cases present in a defined pop.

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19
Q

What does a population at risk exclude

A

Those already w/ the disease
Those who are biologically unable to contract disease

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20
Q

The 3 measures of incidence

A

Count, rate, proportion

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21
Q

Incidence Count

A

Number of new cases in a population (say in 2018)

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22
Q

Incidence Proportion/Fraction

A

of new cases / # of people in population at risk in a given time

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23
Q

What is incidence proportion a measure for?

A

RISK

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24
Q

Cumulatative incidence is a measure of ______ ______ and measures

A

Incidence proportion: measures the number of new cases of a disease occurring during a specific time period
“20% of men develop diabetes before 60th birthday)

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25
Q

Incidence Rate

A

of people who develop case / total person time at risk

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26
Q

When to use incidence rate?

A

When comparing different people/groups in a study for a different amount of time. Assume rate of contraction remains constant

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27
Q

How to calculate Incidence rate?

A

total # of new cases in a period / population at risk x time

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28
Q

Difference between incidence proportion and rate

A

Incidence proportion is over population at risk, incidence rate is person time. Proportion can show if there is an alarmingly large amount of cases given a pop. size, unlike a rate

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29
Q

Attack rate

A

Same as incidence proportion, but usually refers to outbreaks or risks related to particular exposure

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30
Q

Prevalence proportion

A

of people with disease / # of people in at risk pop

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31
Q

Point prevalaence

A

prevalence at particular point in time (convention)

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32
Q

Period Prevalence

A

count/proportion of who had disease at any time within a period

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33
Q

Relationship between incidence and prevalence

A

Prevalence depends on incidence and duration of the disease

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34
Q

_____ is an example of high incidence, low prevalence
_____ is an example of low incidence, high prevalence

A

common cold
chronic heart disease

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35
Q

Illness duration depends on

A

Speed of cure/death

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36
Q

Prevalence is a good measure of ______ but not of _________

A

burden of disease, but not of risk

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37
Q

Prevalence = Incidence x Duration assuming

A

steady state, closed pop, somewhat low prevalence

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38
Q

When is seeing increasing prevalence good

A

For incurable chronic diseases, means life spans are increasing

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39
Q

Problems with Numerator in Morbidity Data

A

Over/under inclusive case definition (must be precise)
Errors/bias in data collection
Changing case detection (better screening procedures)

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40
Q

Problems with Denominator in Morbidity Data

A

Only those AT RISK in denominator
Having strict/precise definitions for sub populations

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41
Q

What does mortality depend on

A

lethality of disease and prevalence

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42
Q

Mortality Count

A

of deaths in a defined pop

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43
Q

Annual mortality rate

A

of deaths in a pop in a year / population size on avg/at year’s midpoint

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44
Q

Cause specific mortality rate

A

of deaths from particular cause/# of people in pop. in time period

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45
Q

Age-specific mortality

A

of deaths in age group/pop of that age group

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46
Q

Years of potential life lost

A

Total yrs of life lost before standard age, measures premature mortality

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47
Q

Excess mortality

A

of rate of deaths observe in pop - expected # of rate of deaths in pop historically

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48
Q

Proportionate mortality

A

of deaths from particular cause in a pop. / total # of deaths in a pop

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49
Q

Case fatality

A

of people who die from disease / number of people who have acquired disease (best for acute time period diseases)

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50
Q

Case fatality rate doesnt measure population impact, it measures _______

A

lethality

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51
Q

5 year survival rate

A

After 5 years, this % of infected survive (denominator should include only people who were diagnosed at least 5 years ago)

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52
Q

Problems w/ mortality data

A

Assigning cause of death may be difficult (immediate, underlying, or contributing causes)
Case definition of cause of death can change
If multiple causes of death, hard to attribute

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53
Q

Life expectancy

A

Crude but actual measure of population level mortality. Very sensitive to early mortality

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54
Q

Prognosis and natural history stages

A
  1. Biological onset
  2. Pathological evidence (if sought
  3. Signs and Symptoms emerge
  4. Seek Case
  5. Diagnosis
  6. Treatment
  7. Outcome (death, cure, disability, control)
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55
Q

Where is the border between non clinical and clinical stages of natural history

A

signs and symptoms

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56
Q

Why might aids diagnoses fall after routine testing is implementing?

A

After people are aware of their status, they may engage in safer sex

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57
Q

Where were hiv outbreaks in dc

A
  1. center city
  2. southeast
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58
Q

Population density contributes to _______ incidence. Lack of transportation contirbutes to ________ incidence.

A

higher, lower

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59
Q

Incidence is the # of cases, not necessarily the number of diagnoses

A

just remember this

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60
Q

For chronic diseases, we actually want prevalence to ______ in the short term

A

increase, indicates longer life spans

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61
Q

What is a sample statistic a best measure of?

A

population parameter

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62
Q

The standard error and CI calcualted from the sample are our best approximations of how much our population parameter would…….

A

vary if we were to draw a different sample in the same manner from the same population

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63
Q

Unlucky sample are

A

always possible

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64
Q

The larger the sample

A

the less random variation we expect, closer to pop. value we expect our sample estimates to be

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65
Q

random (non-systematic error):

A

discordance between calculated sample value and true population value

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66
Q

If we were to take hundreds of samples,

A

any given sample may randomly diverge, but the average value estimated would match the population value

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67
Q

Non-random error

A

everything else besides random sampling error that causes an inaccurate estimate of population value –> LEADS TO BIAS

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68
Q

coverage error

A

over or underinclusive samples

69
Q

systematic sampling error

A

some americans less likely to be selected for sample (like homeless)

70
Q

non-response error

A

not everyone is going to respondmeasurem

71
Q

measurement errors

A

people lie, forget, feel pressure

72
Q

Characteristics of Simple random sampling

A

Everyone in pop has equal % of being selected
Some list of all eligible units
Some way of randomly selecting people

73
Q

There is _____ bias from other sources than random sampling error

A

always

74
Q

How to interpret a 95% confidence interval

A

We are 95% confidence that the interval calculated for our sample contains the true population value, assuming no source of error other than random sampling error.

75
Q

95% confidence interval 3 key aspects

A
  1. Estimation of true pop. value (an interval)
  2. A degree of confidence
  3. Assuming only random sampling error
76
Q

Screening is the basis of ______ prevention

A

secondary

77
Q

Screening is

A

the systematic application of diagnostic test to identify cases and intervene early

78
Q

Screening vs testing

A

Testing is more specified, looking to identify individuals w/condition and initiate intervention

79
Q

Between which stages of the natural history of disease doees screening target

A

Pathological evidence stages and signs/symptoms stage

80
Q

Sensitivity

A

Proportion of people with disease who are positive

81
Q

Specificity

A

Proportion of people who are disease free who test negative

82
Q

PPV

A

If you are positive, what is the probability you actually have the disease.

83
Q

NPV

A

If you are negative, what is the probability you do not have the disease

84
Q

Reliability

A

Test results can be different at times due to
different conditions
who is conducting the test

85
Q

To improve reliability of screening

A

Have very clear screening/testing protocols
-Consistent use of calibrated instrutments
-Training for test admin
Multiple tests/people determining the results

86
Q

Screening without subsequent intervention is

A

pointless and unethical

87
Q

Validity tell us

A

Does a test measure what it is supposed to

88
Q

Two dimensions of validity

A

Accuracy in measuring
Does the thing being measured actually mean anything

89
Q

Two basic forms/results of tests

A
  1. yes/no result
  2. continuous result requiring a cutoff
90
Q

PPV is affected by

A

the specificity of the test (if you don’t have the disease, what proportion test negative)

Prevalence

Because when you have a lot of false positives, this decreases PPV a lot

91
Q

How to increase PPV

A

administer sequential screening tests
1. cheaper, lower sens/spec test
2. most costly, expensive, valid test

or seek higher prevalence populations –> higher risk increases PPV

92
Q

Impacts of increased sequential tests on sensitivity and specificity

A

You only progress if you are positive, so we can eliminate more false positives by doing sequential testing, but we may also generate more false negatives
Sensitivity: reduced, the likelihood of if you have the disease and test positive decreases
Specificity: increased, the likelihood of if you don’t have the disease and you test negative increases

93
Q

When do we care more about PPV?

A

In clinical practice, we want high PPV to avoid overtreating

94
Q

When do we care more about NPV?

A

For highly infecitous and dangerous diseases, we want to make sure people DON’t have the disease. Would be willing to accept some false positives to avoid false negatives (so effectively quanranting more people than needed)e

95
Q

What is surveillance

A

Systematic collection, analysis, and interpretation of health data to help with planning, implementation, and evaluation of public health practice + dissemination
Pointless if not give to public health officials

96
Q

Two major purpose of surveillance

A

Case surveillance
Statistical surveillance

97
Q

Case surveillance

A

Focuses on individuals or groups to identify those w/disease and taken action

98
Q

Statistical surveillance

A

Focuses on pop to identify differentials and trends informing public health policy making –> includes allocation of resources

99
Q

Two major methods of surveillance

A
  1. active
  2. passive
100
Q

Active surveillance

A

extensive efforts by surveillance system to identify cases that have sought care but may not have been reported through normal means

101
Q

Passive surveillance

A

Relies on providers to voluntarily submit public health to authorities

102
Q

Uses for surveillance

A

estimate magnitude of problem, descriptive epi, evaluate disease control measures, facilitate planning, identify individual and local interventions to control diseae

103
Q

Individual level surveillance

A

Case finding, patient tracking

104
Q

Local level surveillance

A

removal of contaminated sources, pollutants

105
Q

Population level

A

Identify issues and form basis for devleoping/implementing targeted programs, public edu, allocation of resources

106
Q

Syndromic Surveillance

A

Focuses on symptoms, not confirmed diagnoses, builds on existing data systems

107
Q

4 principles of surveillance

A

representativeness
timeliness
completeness
sensitivity and specificity

108
Q

What are the major data sources used for surveillance?

A

Infectious disease case reports
Vital Records
Registries
Sentinel Surveillance
Population-based surveys
Medical and administrative records

109
Q

Endenmic

A

Customary presence of disease in pop

110
Q

Epidemic

A

Occurrence of disease in excess of what is normally expected in pop

111
Q

Pandemic

A

Epidemic over a very large geographic range

112
Q

Attack rate

A

Used synonymously w/cumulative incidence proportion of people infected over a short period of time

113
Q

Case-fatality rate

A

Among those who acquire disease, % who die

114
Q

Can case-fatality rate vary?

A

Yes. by pop., risk factors, treatment, and overcrowding

115
Q

Incubation period

A

time from infection to onset of clinical symptoms

116
Q

latent period

A

time from infection to infectiousness

117
Q

Two modes of transmission

A

direct and indirect

118
Q

Direct transmission

A

physical, oral, sex bodies

119
Q

Case definition Levels

A

Suspect, Probably, confirmed

120
Q

A vector moves in between

A

host, agent, and environment (agent is the cause of the disease)

121
Q

Infectious disease transmission requires _____ and ________

A

pathogens and susceptible hosts

122
Q

R0 does NOT measure

A

speed of spread

123
Q

Generation time

A

Average amount of time from primary infection to secondary infection

124
Q

Serial interval

A

Time from primary symptoms to secondary

125
Q

What determines monitoring/quarantining time

A

incubation period

126
Q

Asymptomatic transmissoin

A

transmissions before clinical symptoms develop in the preclinical stage
(icubation > latent)

127
Q

Immunity

A

resistance to infection

128
Q

Natural immunity

A

infection will produce permanent or temp resistance against some pathogen

129
Q

Artificial

A

vaccination and immune system products to produce immunity

130
Q

Sterilizing

A

Protection against effective infection

131
Q

Therapetuic

A

person can be infected against but not seriously

132
Q

R0: the basic reproductin number

A

of secondary infections an infectious person would cause if everyone else in the population was non immune

133
Q

Does each disease have a unique R0

A

No. R0 is depedent on both disase characteristics and interactions of populations

134
Q

Can low R0 and gen time spread faster than high R0 and gen time

A

YES

135
Q

Herd immunity calc.

A

1-(1/R0)

136
Q

Vaccines can be use for 2 purposes

A
  1. protect vulnerable
  2. prevent disease in a pop.
137
Q

Purpose of epidemic control measures

A

Not always to prevent or stop, but to slow it down and srpead it out, buy time for meds and basic science to respond

138
Q

Are epidemic control measures purely scientific?

A

No. Also weigh economic costs and social disruptions

139
Q

Framwork of epidemic

A

Susceptible –> Infectious (some die) –> Recovered (immune)

140
Q

Which three people matter to pathogen

A

susceptible, infectious, recoevered/immune

141
Q

susceptible:

A

able to acquire disease

142
Q

infectious

A

able to spread disease

143
Q

recovered/immune

A

unable to acquire or spread disease

144
Q

Where do new cases come from

A

Transmission-capable interactions between susceptible and infectious people

145
Q

3 ways we can reduce epidemic disease

A

Prevent infectiousness
Minimize/prevent transmission capable interaction between susceptible and infectious
Make susceptible people immune

146
Q

2 purposes of reducing infecitousness

A
  1. decrease # of people who can infect others
  2. reduce likelihood an infected individual will infect contacts
147
Q

How to reduce infectiousness

A
  1. medical treatment
  2. death
148
Q

What to target when preventing transmission capable contact between infectious and susceptible?

A

target mode of transmission
prevent contact or make contact safer

149
Q

Social distancing

A

Closing of schools, businesses, or
places of public gathering.

150
Q

Physicial methods to stop infection

A

masking
handwashing
decontamination of fomites/vehicles
personal protective equipment

151
Q

What do travel restrictions do

A

reduce pop. mixing
prevent cases from entering new pops

152
Q

Isolation

A

separation of patients known or suspected to be infected

153
Q

Qaurantine

A

separation of patients known or believed to be exposed who are not yet sick

154
Q

When is isolation more valuable

A

if disease can be spread casually

155
Q

When is quarantine more valuable

A

disease can be spread before person shows symptoms (asymptomatic tansmission)

156
Q

Isolation requires _____, Quarantine requires ______

A

testing, contact tracing

157
Q

Goal of harm reduction

A

make risky behavior less dangerous
make interactions less transmissoin-capable

158
Q

Goal and tool of making susceptble people immune

A
  1. reduce # of susceptbles infectious can interact with
  2. primary tool is vaccination
159
Q

Outbreak

A

largely synonymous with epidemic, but often implied directly linked and localized cases

160
Q

Case definition

A

working description used to define who is and is not a case
includes clinical/lab criteria and restrictions by time, place, and perosn

161
Q

Case definition should start _____ and end ______

A

broad, narrow

162
Q

Confirm outbreak and find cases

A

what is sounds like

163
Q

Describe the Outbreak using

A

TIme, place, person

164
Q

Develop and Test Hypotheses for outbreak

A

Use info online list and descriptive epi to hypothesize about
exposures
mode of transmission
factors leading to exposure or contamination

165
Q

Line list

A

while investiating cases, make table showing
1. identifying info
2. demographics
3. risk factors
4. Source of reporting

166
Q

Perform environmental or lab investigaitons

A

sampling
lab tesiting
identify pathogens

167
Q

Implement control measures

A

outbreak control!

168
Q

Communicate Preventive Info and findings

A

Provide opp for public educaiton

169
Q

6 steps of outbreak investigation

A
  1. Develop case definition
    2.Confirm outbreak and look for cases
  2. Describe an outbreak by time person place
  3. Develop and test hypotheses
  4. Perform environmental or lab investigations
  5. Implement control measures
  6. communicate preventive info and findings

USPS Midterm 1 (2 decks)

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