Exercises: Sensitivity, Specificity, PPV

Question 1

Sensitivity provides information about the ________ animals

Answer 1

Diseased

(Cannot produce false positive results)
It produces true positives results and false negative results
High sensitivity = many true positives

Question 2

Which type of test produces a lot of false positives ?

1. High sensitivity
2. High specificity
3. Low sensitivity
4. Low specificity

Answer 2

4. Low specificity

True negatives/ (true negatives + false positives) = specificity

Question 3

Which of these correctly describes a very sensitive test

1. Many true positive test results
2. Many false positive test results
3. Few true positive test results
4. Few false positive test results

Answer 3

1. Many true positive test results

Question 4

A high Sensitivity test can have a high specificity

True or false

Answer 4

You can’t tell

Se tells you NOTHING about sp

Question 5

Specificity only deals with _________ animals

Answer 5

Non-diseased

Question 6

Which type of test produces a lot of false negative test results ?

1. High sensitivity
2. High specificity
3. Low sensitivity
4. Low specificity

Answer 6

3. Low sensitivity

Specificity doesn’t have anything to do with false. Negative results

Question 7

Specificity of a diagnostic test is:

A. The proportion of truly diseased animals that test positive
B. The proportion of truly non-diseased animals that test negative
C. The proportion of test-positive animals that are truly diseased
D. The proportion of test-negative animals that are truly non-diseased

Answer 7

B. The proportion of truly non-diseased animals that test negative

(A highly sensitive test; when negative rules disease out)

Question 8

A highly sensitive test ….

A. When positive, rules disease out
B. When positive, rules disease in
C. When negative, rules disease out
D. When negative, rules disease in

Answer 8

C. When negative, rules disease out

Question 9

At a 100% prevalence it doesn’t matter what the spe/Sen. is the PCV will always be 100%

True or false

Answer 9

True

Question 10

PPV provides information about the number of animals that test ______.

Answer 10

Positive

Question 11

The SNAP 4Dx canine test kit produced by IDEXX detects what ?

Answer 11

1. Heartworm antigen
2. Ehrlicia canis
3. Anaplasma phagocytophilum
4. And borrelia burgdorferi antibodies