Measures of Disease Occurrence

Question 1

Risk factor is another word for what?

Answer 1

Determinant of disease.

Question 2

When it comes to measuring disease, epi is concerned with what?

Answer 2

the presence of existing health problems in a pop, the occurrence of new health events in a pop, and their measurement.

Question 3

What is important to define when measuring disease occurrence?

Answer 3

what is being measured, the persons or animals included in said measurement, place or location of the study pop, time period of the study.

Question 4

Who is the study population?

Answer 4

the subjects in the study, usually the sample size from a population.

Question 5

Who is the source pop?

Answer 5

pop from which the subjects were drawn

Question 6

Who is the target pop?

Answer 6

pop to which you may want to generalize your results.

Question 7

What are the most common types of measures in epidemiology?

Answer 7

counts, proportions, ratios, and rates.

Question 8

What does a count represent?

Answer 8

Represents the # of animals w/ a dz. Conveys little info due to lack of denominator.

Question 9

Proportions represent what? Which is the most commonly used proportion?

Answer 9

The number of dzd animals divided by the total # of animals in the study. The #s in the numerator are also in the denominator. Most commonly used: prevalence.

Question 10

What are ratios? Which is the most commonly used in epi?

Answer 10

a fraction in which the numerator is not part of the denominator. Most commonly used: odds.

Question 11

What is a rate?

Answer 11

the # of new occurrences of dz (cases) divided by # of animals in study within a specified time frame.

Question 12

What are the most commonly used rates in epi?

Answer 12

cumulative incidence and incidence rate.

Question 13

What is prevalence?

Answer 13

the proportion of the study pop that is dzd at any one time. Gives you info on how frequently you may see a dz in your practice.

Question 14

What is the difference between point prevalence and period prevalence?

Answer 14

point prevalence: proportion of study pop dzd at a single point in time, while period prevalence is the porportion of study pop dzd during a specified period of time.

Question 15

What is incidence?

Answer 15

the # of new cases of dz that occur in the study pop over time.

Question 16

What does incidence tell you?

Answer 16

the risk of becoming dzd.

Question 17

What information does cumulative incidence tell you?

Answer 17

the likelihood of a susceptible individual in the pop becoming dzd during the study period. All animals were dz free at the beginning of the study.

Question 18

What is an attack rate? What does it tell you?

Answer 18

a specific type of cumulative incidence. It is essentially cumulative incidence during an outbreak. Probability of becoming dzd during the course of an outbreak .

Question 19

When would you use an incidence rate?

Answer 19

When you’ve got animals entering and leaving the population during the study.

Question 20

How is an incident rate expressed?

Answer 20

as the # of cases per animal time at risk (5 cases per 67 cow months at risk, for example)

Question 21

How are period prevalence and cumulative incidence reported?

Answer 21

As cases/animals/time

Question 22

What is the difference between incidence and prevalence

Answer 22

prevalence (new and old cases) measures the amount of disease in a population while incidence measures the rate of dz occurrence (only new cases)

Question 23

What does prevalence depend on?

Answer 23

incidence and duration of disease. The longer old cases hang around sick, the higher the prevalence.

Question 24

Which is best to use to assess increasing or decreasing trends in dz frequency, incidence or prevalence?

Answer 24

incidence

Question 25

Which is best to use to assess the overall burden of a disorder, including the costs and resources?

Answer 25

prevalence

Question 26

Whats the difference between a mortality rate and a case fatality rate?

Answer 26

mortality rate counts the # of deaths from a specific dz during a time period, out of the entire pop during that time. Case fatality rate is those that die during the dz outbreak, out of all the dzd animals.