Measures of Disease Occurrence

Question 1

Study Population

Answer 1

Subjects in the study

Usually a ‘sample’ from a source population

Question 2

Source Population

Answer 2

Population from which the subjects were drawn

Question 3

Target Population

Answer 3

Population to which we may want to generalize our results

Question 4

What are the most common types of measures in epidemiology?

Answer 4

Counts
Proportions
Ratios
Rates

Question 5

Proportion

Answer 5

The count of animals with the disease as a fraction of the total animals that could be diseased

Question 6

Prevalence

Answer 6

the most commonly-used proportion in epidemiology

Question 7

Ratios

Answer 7

A measure of the frequency with which an event occurs in a defined population over a specified period of time
A fraction in which the numerator is not part of the denominator

Question 8

What are the commonly used rates in epidemiology?

Answer 8

Cumulative incidence

Incidence rate/density

Question 9

What are the types of Prevalence?

Answer 9

Point prevalence

Period prevalence

Question 10

What are the types of incidence?

Answer 10

Cumulative incidence

Incidence rate

Question 11

Attack rate

Answer 11

a specific type of cumulative incidence

Question 12

Prevalence

Answer 12

the proportion of the study population that is diseased at any one time

Question 13

Point Prevalence definition

Answer 13

The proportion of the study population that is diseased at a single point in time

Question 14

What is the most common measure of prevalence?

Answer 14

Point Prevalence

Question 15

Period Prevalence definition

Answer 15

the proportion of the study population that is disease during specified period of time

Question 16

Incidence

Answer 16

the number of new cases of disease that occur in the study population over time
The rate of occurrence of new diseases in that study population

Question 17

Cumulative incidence

Answer 17

the proportion of disease free (susceptible) individuals in the study population who became diseased during a specified period of time

Question 18

Assumption with cumulative incidence

Answer 18

all individuals in that study population are at risk of getting the disease (or other outcome) of interest
Every individual in the study population is assessed at the start study, to identify and remove existing cases
The entire population at risk must be followed from the start of the study until the end

Question 19

Attack Rate

Answer 19

a specific type of cumulative incidence

cumulative incidence during an outbreak

Question 20

Incidence rate

Answer 20

instantaneous rate of occurrence of new cases of disease among non-diseased animals in the population
Expressed as the number of cases per animal-time at risk

Question 21

Disease risk

Answer 21

the probability of becoming diseased

Question 22

at risk

Answer 22

an individual is not diseased and is capable of becoming diseased

Question 23

Risk Factors

Answer 23

factors that increase the probability of becoming diseased

Question 24

Exposure to a risk factor

Answer 24

an individual has come in contact with a risk factor or has the risk factor (while not diseased)

Question 25

Mortality rate

Answer 25

the incidence of death in a given time period

Question 26

Case Fatality rate

Answer 26

The number of cases of a specific disease that are fatal, within a specified time following disease onset or diagnosis