Exam 1: Frequency of Clinical Events

Question 1

What are the epidemiologic health care levels?

Answer 1

Primary care
Secondary care
Tertiary care

Question 2

What does primary care action to do?

Answer 2

Prevent disease

Question 3

What does secondary care action to do?

Answer 3

Detect disease early with intention to reduce impact

Question 4

What does tertiary care action to do?

Answer 4

Extend/improve life after diagnosis

Question 5

What is the generalized disease pathway associated with primary care?

Answer 5

Induction: exposure, interaction, undetectable

Question 6

What is the generalized disease pathway associated with secondary care?

Answer 6

Incubation latent period: local onset, detectability

Question 7

What is the generalized disease pathway associated with tertiary care?

Answer 7

Signs: systemic affect, clinical manifestation, tissue destruction

Question 8

What are the experimental methods in epidemiology?

Answer 8

True experiments
Quasi-experiments
Observational studies

Question 9

What are true experiments?

Answer 9

Subjects are randomized to treatment and receive specific treatments (randomization and control)

Question 10

What are quasi-experiments?

Answer 10

Like a true experiment except no randomization (control without randomization)

Question 11

What are observational studies?

Answer 11

Neither randomization nor control

Subjects self select their treatment

Question 12

What are the observational study types?

Answer 12

Cohort
Case-control
Cross sectional
Others (ecologic, hybrid, spatial time clusters, family clusters, nested/ambidirectional)

Question 13

What are measures of disease frequency?

Answer 13

Rate

Risk

Question 14

What are measures of association?

Answer 14

Assessing risk factor: disease
Age, breed, sex, production cycle
Relative risk, odds ratio, incidence density ratio

Question 15

What are measures of disease impact?

Answer 15

Attributable risk, attributable difference, population attributable risk
Assess impact of exposure in the populaiton

Question 16

Describe incidence

Answer 16

An expression of the force of disease
Applied to new cases in a period
A person can be an incidence case only once
Indicates the movement from well to diseased

Question 17

What are the 2 ways to express incidence?

Answer 17

Incidence rate (incidence density)
Cumulative incidence (risk, incidence proportion, attack rate)

Question 18

What is rate?

Answer 18

An expression to describe a change in one quantity with respect to another quantity with the denominator featuring a time component

Question 19

What is the denominator unit of rate?

Answer 19

Animal-time

Question 20

How do you calculate incidence rate?

Answer 20

No. of new cases over a time period / the sum, over all individuals, of the length of time at risk of developing disease

Question 21

How do you count animal time?

Answer 21

Only count time of non-disease animals. Once diseased, time does not count

Question 22

What are situations that you would stop counting animal time?

Answer 22

Animal gets disease
Death from another cause
Removed from herd
Study terminates
Animal undergoes intervention to render it non-susceptible

Question 23

What is simple cumulative incidence?

Answer 23

Also termed risk or incidence proportion

Proportion of non-diseased individuals at the beginning of a period of study that becomes diseased during the period

Question 24

How must individuals start when calculating simple cumulative incidence?

Answer 24

They must start out non-diseased in order to be at risk for the new disease

Question 25

How do you calculate simple cumulative incidence?

Answer 25

No. of new cases over a period of time / No. of healthy animals at beginning of time period

Question 26

What is attack rate?

Answer 26

A cumulative incidence rate for an outbreak
The numerator is the number of new cases and the denominator is the number of individuals exposed at the start of an outbreak or for a limited time

Question 27

When is attack rate appropriate?

Answer 27

When the exposure occurs in a very short and defined period of time (food poisoning, neonatal period, acute exposure to radiation)

Question 28

How do incidence rate and cumulative incidence differ?

Answer 28

IR (0.03 cases/cow-day)
Precise expression of disease force
Applicable to a group
100 animal-years can be accumulated several ways
Hard to interpret, so less often used than CI

CI (20%)
Very easy to interpret
Applicable to group or individual
Problematic when animals are lost in the time window
Similar to IR, reflects an overall average disease force in the time window

Question 29

What is a dangling numerator?

Answer 29

Reporting the number of cases without considering all other animals that are at risk in the denominator