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22 Cards in this Set
- Front
- Back
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Formula for Attack rate
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# with risk and disease
___________________ # at risk |
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What is used in outbreak situations to determine source of agent and disease?
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Attack rate for each food served
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What are the challenges for determining the source of an outbreak?
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Correlated consumption
Cross-contamination Recall Quanity Susceptibility |
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What is ASSOCIATION?
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in Epi, look for association between exposure and disease.
Is association valid? Is there evidence for causality? |
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What is meaning of association?
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Disease (outcome) is more/less common in people more/less exposed to some "agent"
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Important rules of association
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If exposure causes an OUTCOME - then always an assn
If an exposure and an outcome are ASSOCIATED, then - there may be a causal association - the assn MAY BE DUE TO *Bias *Confounding |
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What are sources of Epidemiologic Data?
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*Specifically collected data
- epi studies *Data collected for gen purposes - dis surveillance - hosp/clinic records - ins records - employer and school records - special surveys - vital records |
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What are MEASURES of epi
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1. (Point) prevalence
2. Cumulative incidence a. Attack rate b. Period Prevalence 3. Incidence rate (incidence density) |
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What is Point Prevalence?
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How much disease exists?
N=size of population(at risk) x= Number of cases in pop. Prevalence=x/N(x/N*100%)- either % or proportion |
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example of point prevalence
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23.6 mil people - 7.8% have diabetes
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What does Cumulative Incidence describe?
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How high is the risk?
This is 2. under Measures |
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Equation for CI
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N=size of population at risk
x=Number of NEW cases T=time period of new cases T CI=x/N ((x/N*100%) |
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Use CI to describe a disease situation
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The 10 year CI of dental caries was 0.4
CI=Risk |
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What is 1. under measures
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1. Point Prevalencd - how much disease does EXIST
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2a. Under Measures describes Attack Rate. Formula?
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2.Cumulative Incidence
a. Attack Rate AR=x/N (x/N x 100%) During Time period (implicit for plausible incubation period) |
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Give example of ATTACK RATE
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2 out of 144 passengers developed H1N1 influenza
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Describe PP (Period Prevalence)
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N=size of pop at risk at beginning of F/U
x= number of existing and new cases T= time period of follow-up T PP=x/N (x/N x 100%) |
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Give example of Period Prevalence
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30% had the flu during 2008/09 flu season
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What does Incidence Rate describe?
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How frequently does the disease/outcome develop
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What is formula for IR
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pt = # of persons at risk during time of observation
x = Number of cases arising from persons at risk during time of observation IR = x/pt |
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What do incidence rates measure
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Natural measure of frequency( = number of events per population per time)
A rate is normalized so should be independent of number of people or length of time observed. |
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Example of Incidence Rate
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'in 2006, the incidence of diabetes in Texas was 10.2 per 1000 population'
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