Random facts (epidemiology, etc)

Question 1

Define sensitivity

Answer 1

• The likelihood of a positive test result in a patient affected with the disease (a true positive)
• Higher the sensitivity, the lower the false negative rate (so if they test negative, it’s believable)
• Used to RULE OUT a disease (screening test)

Question 2

Define specificity

Answer 2

• The likelihood of a negative test result in a patient not having the disease (true negative rate)
• Higher the specificity, the lower the false positive rate (so if they test positive, it’s believable)
• Used to CONFIRM a diagnosis

Question 3

Define positive predictive value

Answer 3

• The chance that a patient with a positive test result has the disease
• Good confirmatory tests
• Usually correlates with specificity when the disease prevalence is low

Question 4

Define negative predictive value

Answer 4

• The change that a patient with a negative test result does not have the disease
• Good screening tests
• Usually correlates with sensitivity when the disease prevalence is high

Question 5

What do PPV and NPV depend on?

Answer 5

Disease prevalence