Epidemiology and Pan-Systemic

Question 1

What is an odd’s ratio

Answer 1

Measure of association between an exposure and an outcome

OR = (A/B)/(C/D)
OR= 1 –> variable does not correlate to disease
OR > 1 –> variable increases odds of disease
OR < 1 –> variable decreases odds of disease

Question 2

Sensitivity

Answer 2

Ability of a test to correctly identify patients with a disease
Sn = [a/(a+c)]x100

Question 3

Specificity

Answer 3

ability of a test to correct identify patients without disease
Sp = [d/(b+d)]x100

Question 4

Positive Predictive Value

Answer 4

The probability that a patient with a positive (abnormal) test result will actually have the disease

PPV = [a/(a+b)]x100

Question 5

Negative Predictive Value

Answer 5

The likelihood that a patient who has a negative test result does not have the disease

NPV = [d/(c+d)]x100

Question 6

Calculating Incidence

Answer 6

(new cases)/(populations at risk in time period)

Question 7

If an animal is going to be euthanized based on results, do you have a test with high specificity or sensitivity?

Answer 7

Want a test with very high specificity
- specific tests have few false positives, will confirm the disease

Question 8

Does a good screening test have high specificity or sensitivity?

Answer 8

Want high sensitivity

Question 9

Does a good diagnostic/confirmatory test have good specificity or sensitivity?

Answer 9

Has high specificity

Question 10

How are prevalence and positive predictive values related?

Answer 10

As prevalence decreases, the PPV of the test decreases