Flashcards in Measure of Disease Occurrence Deck (61)

1

## why measure disease?

###
know what is going on in a population and how disease is changing it

compare disease in groups

2

## T/F "risk factor" is another word for "determinant" of disease

### true

3

## epidemiologist are concerned with

###
presence of existing health problems in a population

occurrence of new health events in a population

and their measurement (quantification)

4

## what do epidemiologists measure

###
amount of disease in a population at one point in time or over a period of time

change in amount of disease in a population over a period of time

5

## stratified=

### population subdivided by group (breed, age, sex etc)

6

## what should be defined when measuring disease occurrence

###
what is being measured

study population

place of location of study population

time period of study

7

## study population

###
subjects of the study

usually a sample from the "source" population

8

## source population

### population from which subjects were drawn

9

## target population

### population to which we may want to generalize our results

10

## most common types of measurement used

###
counts

proportions

ratios

rates

11

## counts

###
number of animals that have a disease

convey little information on their own

12

## proportions

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

diseased animals/ total in study

13

## what is the most commonly used proportion in epidemiology

### prevalence

14

## ratios

###
fraction which the numerator is not part of the denominator

measure of frequency with which an event occurs in a defined population over a specified period of time

expression of the change in the amount of disease in a defined population per unit of time

15

## what is a commonly used ratio in epidemiology

### 'odds' ratio

16

## 2 types of prevalence

###
point

period

17

## 2 types of incidence

###
cumulative incidence

incidence rate

18

## what is prevalence?

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

amount of disease in the population at any one time

19

## T/F prevalence provides information about how frequently you might expect to see the condition in your practice

### true

20

## point prevalence

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

21

## what is the most common measurement of prevalence

### point prevalence

22

## how is point prevalence determined

### cross-sectional studies

23

## how do you calculate point prevalence

###
number of cases of disease in the population at a particular time

--------------------------------------------total population

24

## what can point prevalence be expressed as

###
percent

proportion

fraction

25

## what is period prevalence

### proportion of the study population that is diseased during a specified period of time

26

## T/F period prevalence includes old and new cases

###
true

doesnt tell us about when the animals became diseased

27

## T/F period prevalence is the probability that an animal in the study population is diseased during the period of the study

###
true

28

## how do you calculate period prevalence

###
number of cases of diseased patients over a period of time

--------------------------------------------

total population over that period of time

29

## what is incidence

### number of new cases of disease that occur in the study population over time

30

## T/F incidence tells us how frequently non-diseases/susceptible individuals become diseased over time

### true

31

## incident cases=

### new cases of disease

32

## incidence is interpreted as...

###
probability of a disease-free animal from the study population becoming diseased

risk of becoming diseased

33

## how do you calculate cumulative incidence

###
number of new cases

------------------------------------------

total population at risk

34

## What is cumulative incidence?

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

35

## how is cumulative incidence interpreted

### probability (risk) of a susceptible individual in the study population becoming diseased during the study period

36

## how is cumulative incidence expressed

###
a number

dimensionless

37

## what are the assumptions with cumulative incidence

###
all individuals in the study pop are at risk of getting the disease of interest

every individual in the study pop is assessed at the start of the study

entire population must be followed from the start of the study until the end

38

## attack rate

###
cumulative incidence during an outbreak (specific type of cumulative incidence)

applied to a narrowly-defined population

39

## how is attack rate interpreted

### probability (risk) of becoming diseased during the course of an outbreak

40

## how do you calculate attack rates

###
number of new cases

------------------------------------------

total population at risk (exposed)

41

## how is cumulative incidence can be expressed

###
number

dimensionless fraction

may not have a reference to time as it is assumed to be the duration of the outbreak

42

## what is incidence rate

### instantaneous rate of occurrence of new cases of disease among non-diseased animals in the population

43

## when is incidence rate used

### when animals are entering and leaving the population

44

## T/F incidence rate can be easily interpreted at the individual animal level

### false

45

## how do you calculate incidence rate

###
number of new cases

------------------------------------------

sum of the length of time

46

## incidence rate is expressed as

### number of cases per animal-time at risk

47

## T/F ONLY the incidence rate is reported as animal-time at risk

###
true

period prevalence and cumulative incidence are reported as cases/animals/time

48

## prevalence vs incidence

###
prevalence: measure of amount of disease in a population

incidence: measure of the rate of disease occurrence

49

## relationship between prevalence and incidence

### a new case (incidence case) becomes and old case (prevalent case) and remains so until recovery or death

50

## T/F the prevalence of a disease may increase when incidence remains stable but survival of cases improves

### true because reasons

51

## which is used for chronic conditions

### prevalence

52

## used to assess causes for disease

### incidence

53

## best measure to assess increasing or decreasing trends in disease frequency

### incidence

54

## disease risk

### probability of becoming diseased

55

## at risk

### means individual is not diseased an is capable of becoming diseased

56

## risk factors

### factors that increase the probability of becoming diseased

57

## exposure to a risk factor

### individual has come into contact with a risk factor or has the risk factor (while not diseased)

58

## mortality rate

### incidence of death in a given time period

59

## how to calculate mortality rate

###
number of deaths during a specified time period

------------------------------------------

total population

60

## case-fatality rate

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

61