Veterinary Epidemiology And Diagnostic Tests

Question 1

What is veterinary epidemiology?

Answer 1

Study of distribution and determinants of health related states/events in specified populations, and the application of this study to control health problems

Question 2

What type of study decides cases in relation to number at risk ?

Answer 2

Descriptive epidemiology

Question 3

What type of study finds determines associations between exposure and outcomes ?

Answer 3

Analytical

Question 4

Case report, case series, and cross sectional studies are what type of study?

Answer 4

Descriptive

Question 5

T/F: case reports cannot identify associations and outcome, or infer causality

Answer 5

True

Descriptive study- nothing is compared- can only generate hypotheses for future testing

Question 6

T/F: epidemiological studies can be used to determine cause of disease

Answer 6

False

Can only determine an association-> given exposure and frequency, cause can be inferred

Question 7

What are the models of causation?

Answer 7

Epidemiological triad

Rothmans model (causal pies)

Bradford-hill criteria

Question 8

What is the epidemiological triad?

Answer 8

Environment
Host
Agent
-> useful except in dz without any single necessary factor, but can have many contributing factors

Question 9

What is Rothmans model?

Answer 9

Many factors, when host is exposed to all, disease will occur
(Causal pies)

Compete pie => sufficient cause for disease

Question 10

In Rothmans model, a component that appears in every pie is considered a ____________ factor

Answer 10

Necessary

Question 11

What is the Bradford-hill criteria?

Answer 11

Temporal (cause before effect) 
Dose-dependent 
Repeatable 
Specificity of exposure 
Cessation of exposure -> no disease

Question 12

What type of diagnostic test gives a yes/no answer

Answer 12

dichotomous test

Eg presence or absence of disease

Question 13

What type of diagnostic test gives a result on a continuum?

Answer 13

Continuous

Eg. Serum/CBC/titers/Chen

Question 14

What is the “cut off value” for a diagnostic test?

Answer 14

Value at which test values on one side are positive and on the other are negative

Question 15

How is the cut off value determined?

Answer 15

Experimentally -> value that gives the least amount of false positives and false negatives

Question 16

Non diseased animals that test positive =

Answer 16

False positive

Question 17

Diseased animals that test negative

Answer 17

False negatives

Question 18

__________________ is the true disease status of an individual determined by this test which is very accurate and reliable

Answer 18

Gold standard test

Question 19

A very _________ test, when _________ rules disease OUT

Answer 19

Sensitive; negative

Question 20

A very ___________ test, when _________ rules disease IN

Answer 20

Specific; positive

Question 21

If a test has 100% sensitively it means…
A. All negative tests are true negatives
B. All positive test results are true positives

Answer 21

A. All negative tests are true negatives

Question 22

If a test is 100% specific, this means…
A. All negatives are true negatives
B. All positives are true positives

Answer 22

B. All positives are true positives

Question 23

We should used a highly ________ test when there is high cost associated with false postives

Answer 23

Specific

Question 24

We should used a highly __________ test you want to prevent any diseased animals from entering the country

Answer 24

Sensitive

Question 25

What is the logic behind testing in series?

Answer 25

Use a highly sensitive test -> all positives

Test them with a highly specific test -> rule out any false positives

Question 26

Sensitive is the probability of a diseased animal testing ______

Answer 26

Positive

Question 27

Specificity is the probability of an non-diseased animal testing __________

Answer 27

Negative

Question 28

What does the positive predictive value tell us?

Answer 28

Probability of a positive test being a truly diseased animal

Question 29

What does the negative predictive value tell us?

Answer 29

The probability that a negative test is a truly non-diseased animal

Question 30

How do we find the PPV?

Answer 30

PPV = true positive/test positives

Question 31

How do we find the negative predictive value?

Answer 31

NPV= true negatives/test negatives

Question 32

T/F: Sensitivity and specificity change with prevalence of disease in population.

Answer 32

False

-> PPV and NPV change with prevalence