1. Objectives of epidemiology.2-7
Step 1. Understanding the etiology or cause of a disease (risk factors)
Step 2. Finding out the extent that a disease or health problem affects a
community or population.
Step 3. Determine the natural history or prognosis
Step 4. Evaluate existing and newly developed preventative therapeutic
measures and modes of healthcare delivery
Step 5. Provide the foundation for developing public policy relating to
environmental problems, genetic issues, and other considerations regarding
disease prevention and health promotion.
2. Define, compare, calculate, and interpret Measures of Morbidity .41.58
a. Incidence rate.41.51
(# of NEW cases of a disease occurring in the population during a
specified period of time / # of persons who are at risk of developing
the disease during that period of time) x 1000 = Incidence rate per
1,000
: the NEW cases of a disease over a period of time.
b. Attack rate.46
- special form of cumulative incidence
- Used for diseases of short observation time period
- Not a true rate because the time dimension is often uncertain (food
borne outbreaks)
= (# of new cases among population during period / population at risk
at beginning of period) x 100 (expressed as %)
c. Prevalence.46
: the EXISTING cases of a disease over a period of time.
(# of cases of a disease present in the population at a specified time / #
of persons in the population at that specified time) x 1,000 =
Prevalence per 1,000
3. Understand why incidence data are important for measuring risk.
Measures risk (probability of developing disease)
Useful for investigating determinants of disease (not survival)
To investigate causes of disease
Need to know population ‘at risk’ or ‘person-time’ at risk
4. Define, compare, calculate, and interpret Measures of Mortality
a. Cause-specific mortality rate.64.65
=(Total number of deaths due to x cause / total population at mid
year) x 1,000
, =(No.of deaths from leukemia in one year in children younger than 10
years of age / No.of children in the population younger than 10 years
of age at midyear) x 1,000
b. Annual mortality rate .64
-annual death rate, or mortality rate from all causes.
(total # of deaths from all causes in 1 year / total population at mid
year ) x 1,000
c. Case-fatality.65
--what percentage of people who have a certain disease die within a
certain time after their disease was diagnosed?
=(# of deaths due to a certain disease/total # suffering from that
disease) x 100 %
-Measure of the severity of the disease
-As therapy improves, case-fatality would be expected to decline.
d. Proportionate mortality. This is Not a rate. 66
-the proportionate mortality from cardiovascular disease in the U.S. in
2010 (percent, %)
-of all deaths in the US, what proportion was caused by cardiovascular
disease?
=( # of deaths from cardiovascular diseases in US in 2010 / total
deaths in the US in 2010) x 100
5. Assess the Validity.89 and Reliability105.110 of Diagnostic and Screening
Tests
a. Define, compare and calculate measures of validity, including
sensitivity and specificity.
-Validity of test: its ability to distinguish between who has a disease
and who does not.
-Sensitivity of test is defined as the ability of the test to identify
correctly those who have the disease.
-Specificity of test is defined as the ability of the test to identify
correctly those who do not have the disease.
Have a Disease Do not have
Disease
Positive True Positive False Positive Positive
(TP) (FP) predictive value
Have the Do not have the =
disease disease (TP/TP+FP)x100
And test But test =(a/a+b)x100
positive positive
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