Epidemiology

Question 1

Proportion

Answer 1

fraction or percentage

ex. 1/500 AA babies have sick cell
ex. 85% of babies born with hemophilia have type A

Question 2

Ratio

Answer 2

number and denominator are NOT related

ex. males vs. females, urban vs. rural

Question 3

Rate

Answer 3

has time component or person time

ex. 10 cases of hepatitis per 500 students per year

Question 4

Calculating Populations at Risk

Answer 4

Populations are dynamic
births and deaths
immigration, emigration

Affected and immune individuals (not at risk)

Removal from at-risk population
cases (prompt recognition)
loss to follow up
death due to other causes (competing risks)
change in risk status (hysterectomy and uterine cancer)

Question 5

Incidence vs. Prevalance

Answer 5

Incidence Measures: Based on new cases
Cumulative incidence (incidence proportion)
Incidence rate (incidence density)

Prevalence Measures: Based on existing cases
Point prevalence- occurs at specific point
Period prevalence- occurs at certain period in time

Question 6

Attack Rate

Answer 6

Measurement of people exposed to a variable who were affected compared to the total population that was exposed whether they were affected or not

ex. # of people exposed to F that fell ill / # of people exposed to F

Question 7

Attributable Risk

Answer 7

The incidence of disease in the exposed population whose disease can be attributed to the exposure

incidence of exposed - incidence of unexposed

Question 8

Attributable Risk Percentage

Answer 8

The proportion of disease in the exposed population whose disease can be attributed to the exposure

(incidence of exposed - incidence of unexposed) / incidence of exposed

(Ie - 1) / Ie