Epidemiology: Disease in Populations

Question 1

Risk Factor

Answer 1

Variable associated with an increased risk of disease or infection

Question 2

Protective Factor

Answer 2

Variable associated with a decreased risk of disease or infection

Question 3

What are Hill’s Criteria of Causation?

Answer 3

The time sequence of the events
The strength of the association
Biological gradient
Consistency
Compatibility with existing knowledge

Question 4

Component Cause

Answer 4

Any causal factor (host, agent, environment)

Question 5

Necessary Cause

Answer 5

A component cause that is required for disease to occur

Question 6

Sufficient Cause

Answer 6

A set of component causes that is capable of causing disease
When sufficient cause is present, disease CAN occur

Question 7

Causation

Answer 7

A true mechanism leads from exposure to disease

Question 8

Association

Answer 8

An identifiable relationship between exposure and disease
Exposure might cause disease

Question 9

Confounding Bias

Answer 9

Failure to account for a 3rd/unknown variable design/analysis

Question 10

In general, what is included in a 2x2 table?

Answer 10

Question 11

Relative Risk

Answer 11

Risk of disease in exposed relative to unexposed
Used in most study types (except case-control studies)

Question 12

Give the data, calculate the relative risk

Answer 12

Question 13

Odds Ratio

Answer 13

Ratio of probability of an event occurring to the probability of event not occurring
The odds of disease in exposed compared to odds of disease in non-exposed
Used in case-control studies
OR = AxD/CxB

Question 14

Given the data, calculate the odds ratio

Answer 14

Question 15

How are RR and OR interpreted?

Answer 15

Question 16

What is the relationship between OR and RR?

Answer 16

Question 17

Chi Square Test

Answer 17

A statistical test used to determine whether your experimentally observed results differ from null hypothesis (no effect)
Use when you have categorical variables
Data are frequencies (counts) rather than numerical scores
Measure the difference between the actual counts and expected counts
Test the independence of 2 variables

Question 18

95% confidence interval

Answer 18

The potential range, around the estimate, in which the real value lies

Question 19

Attributable Risk

Answer 19

Risk of disease in exposed due to exposure
AR = Risk in exposed - risk in unexposed

Question 20

Given the data, calculate AR

Answer 20

Question 21

Attributable Fraction

Answer 21

The proportion of disease in exposed due to exposure

Question 22

Given the data, calculate AF

Answer 22

Question 23

Answer 23

Question 24

Question 25

What is the first step in outbreak investigation?

Answer 25

Determine if there is indeed an outbreak

Question 26

What metric is commonly used to identify at risk groups at the start of an outbreak?

Answer 26

Attack rate

Question 27

One of your clients has multiple horses with diarrhea. There are a total of 15 horses on property and they share both pens and fencelines. Before calling you she had seen diarrhea in 4 that share an outdoor pen but all others were fine. When you arrive at the farm ~24h later you count 9 total with diarrhea, including the original 4. Which of the following best represents the daily incidence of the disease?

Answer 27

5

Question 28

It can be challenging to tell the difference between a causal relationship and an association between factors that is not causal. What are the reasons regarding the need to correctly understand the relationship between risk/protective factors and disease:

Answer 28

There exists the potential to waste money on ineffective treatment or preventive efforts
There exists the potential to do harm with inappropriate treatment or preventive efforts
There exists the potential to fuel dissemination of misinformation

Question 29

Many diseases have more than one contributing factor and veterinarians need to make informed decisions to develop effective intervention strategies. What factor type would be most ideal to target:

Answer 29

Necessary factor

Question 30

It is appropriate to use relative risk as a key epidemiological metric for all study types EXCEPT:

Answer 30

Case control

Question 31

You are asked to consult on an investigation of suspected intentional poisoning of dairy cattle with mycotoxins in moldy feed. There has already been a complete investigation conducted through the department of agriculture, a private consultant and law enforcement as the producer claims that the toxin was introduced by an unhappy ex-employee. The investigation showed that animals fed the feed sourced by that employee were 1.4 times more likely to have disease than animals fed other feed (RR = 1.4 with 95% confidence interval of 0.2-6). Based on this information you conclude that:

Answer 31

The available information does not support the feed in question being the source of the problem