Epidemiologic Indices (2)

Question 1

Why do we address epidemiologic indices or measures?

Answer 1

they provide information the frequency of a disease or condition

association between exposures and health outcomes - strength of those relationships

Question 2

What is the Natural History of Disease?

Answer 2

the course of disease from its beginning to its final clinical endpoints

while complete understanding is not necessary for treatment and control, it does facilitate better interventions

Question 3

What is the Natural History of Disease synonymous with?

Answer 3

a disease’s ecology

Question 4

What are the phases of natural history of disease?

Answer 4

preclinical phase
clinical phase

Question 5

What are the benefits of early control of zoonotic disease?

Answer 5

cost-effective and preventive for human disease

Question 6

In zoonotic diseases, [animals/humans] are exposed first

Answer 6

animals

Question 7

What is the Population at Risk (PAR)?

Answer 7

those members (animal or human) of the overall population who are capable of developing disease or condition being studied

*extremely important concept in epidemiology

Question 8

What are common epidemiologic measures?

Answer 8

proportion
percentage
rate

ALL are ratios

Question 9

What is a ratio?

Answer 9

the value obtained by dividing one quantity by another

Question 10

What does a ratio in epidemiology usually imply?

Answer 10

that the numerator is not a subset of a denominator (there are exceptions)

Question 11

What is a proportion?

Answer 11

a type of ratio in which the numerator is part of the denominator

Question 12

What is a percentage?

Answer 12

a proportion that is multiplied by 100

Question 13

A rate is a type of ______. How does it differ from a proportion? What are common rates in epidemiology?

Answer 13

type of ratio

differs because the denominator involves a measure of time

incidence rate, prevalence rate, case fatality rate

Question 14

What is incidence?

Answer 14

refers to the occurrence of new disease or mortality within a defined period of observation (week, month, year, or other time period) in a specified population

Question 15

What is not counted in an incidence?

Answer 15

cases that exist at the beginning of the period

Question 16

What is an incidence rate?

Answer 16

a rate formed by dividing the number of new cases that occur during a time period

by the number of individuals in the population at risk

Question 17

What is incidence rate used to compare?

Answer 17

used to compare risk between similar populations

Question 18

What is the incidence rate formula?

Answer 18

number of new cases in an time period / total population at risk

x 10^n

Question 19

30 cats were negative for FIV at the beginning of the year. At the end of the year, 3 of them tested positive. What is the incidence? What is the incidence rate?

Answer 19

incidence: 3

incidence rate: 3/30 x 100% = 10%

Question 20

What is prevalence?

Answer 20

the number of existing cases of a disease or health condition

or deaths in a population at some designated time (regardless of when they started)

Question 21

10 infected dogs with parvovirus were treated, 7 successfully, and 3 new cases arose of the 50 total. What is the incidence, incidence rate, and prevalence at the end of the year?

Answer 21

incidence: 3
incidence rate: 3/50 = 6%
prevalence: 6 (3 unsuccessful, 3 new)

Question 22

What is prevalence vs incidence?

Answer 22

prevalence: the number of existing cases of disease in the population during a defined period

incidence: the number of new cases of disease that develop in the population during a defined period

Question 23

Incidence and prevalence can be related. What causes prevalence to increase?

Answer 23

increase in incidence
longer duration of the case
in-migration of cases
prolongation of life of patients without a cure

Question 24

Incidence and prevalence can be related. What causes prevalence to decrease?

Answer 24

decrease in incidence
shorter duration of disease

Question 25

What is Attack Rate?

Answer 25

basically, an incidence rate applied to a narrow population over a narrow time period

Question 26

What is the morbidity rate numerator?

Answer 26

the total # of illnesses in a population over a specified period of time

Question 27

What is the Attack Rate equation?

Answer 27

new cases in the time period / population risk at beginning

x 10^n

Question 28

What is the morbidity rate denominator?

Answer 28

average number in a population during a time period

Question 29

What is the mortality rate numerator?

Answer 29

the total # of deaths in a population over a specified period of time

Question 30

What is the mortality rate denominator?

Answer 30

average number in a population during a time period

Question 31

What is Case Fatality Rate?

Answer 31

the number of deaths due to a disease that occur among persons who are afflicted with that disease

Question 32

What is the formula for Case Fatality Rate?

Answer 32

number of deaths due to disease X / number of cases of disease X

x 100

Question 33

In the United States, health officials get concerned with a CFR greater than __

Answer 33

2%

Question 34

What is a risk factor?

Answer 34

a characteristic of value in predicting risk

ex. obesity with breed, sex, age, weight, activity, nutrition, and genetics

Question 35

What is Absolute Risk?

Answer 35

the rate of occurrence

Question 36

What is Absolute Risk the same as?

Answer 36

incidence

Question 37

What is relative risk?

Answer 37

incidence rate among exposed / incidence rate of among not exposed

Question 38

What is attributable risk?

Answer 38

incidence rate exposed - incident rate of unexposed

Question 39

In 2018, 4 of 23 cows developed mastitis. What is the absolute risk of mastitis in this herd? Incidence? Incidence rate of mastitis?

Answer 39

absolute risk: 4
incidence: 4
incidence rate: 4/23 = 17.9%

Question 40

What is the attributable risk of 45 exposed people and 30 people unexposed?

Answer 40

exposed - unexposed

45 - 30 = 15