Epidemio Flashcards
A test is developed that detects the presence of disease X in an animal population. The sensitivity of this test is 0.89 and the specificity is 0.77.
As the prevalence of disease X increases, which one of the following is TRUE?
A. Predictive value of a negative test will increase
B. Predictive value of a positive test will increase
C. Sensitivity of the test will increase
D. Specificity of the test will increase
B. Predictive value of a positive test will increase
Ref: Smith RD, Veterinary Clinical Epidemiology, 3rd edition (2006) pp. 33-51.
A new test is evaluated for the detection of coronavirus. Sixty patients are evaluated that have similar clinical signs: 30 with coronavirus and 30 without coronavirus.
If the sensitivity of the test is 66% and the specificity is 50%, how many patients show a NEGATIVE TEST?
A. 10
B. 15
C. 20
D. 25
D. 25
Ref: Smith RD, Veterinary Clinical Epidemiology 3rd p. 36.
In a test of drug efficacy, the assumed null hypothesis is that the test drug is no better or worse than placebo.
If a statistical test comparing response to drug versus response to placebo has a calculated P value of .001, what is a logical conclusion?
A. The response to drug is better than response to placebo.
B. The response to drug is different than the response to placebo.
C. The response to drug is the same as response to placebo.
D. The response to drug is worse than response to placebo.
B. The response to drug is different than the response to placebo. Ref: Veterinary Clinical Epidemiology 3rd Ed pp138-9.
You are developing a point-of-care test for C-reactive protein for the diagnosis of infectious, inflammatory or neoplastic diseases in dogs, and have just finished your pilot study. You enrolled 73 dogs, of which 16 were healthy and 57 were diseased.
You find that 11 dogs were misdiagnosed by the test: 2 healthy dogs tested positive and 9 diseased dogs tested negative. What is the positive predictive value of your test?
a. 84%
b. 61%
c. 77%
d. 88%
c. 77%
Under which situations would you choose a test with a high sensitivity?
a) If we are testing for a disease with a high prevalence
b) If we are testing for a disease that is rare or foreign
c) If the consequences of having a FP are grave
d) If we intend to rule in (confirm) a disease
b) If we are testing for a disease that is rare or foreign
Which of the following factors is most likely to increase the positive predictive value of a test?
a) Testing for a disease with a low prevalence, and using a test with a high specificity
b) Testing for a disease with a low prevalence, and using a test with a low specificity
c) Testing for a disease with a high prevalence, and using a test with a high specificity
d) Testing for a disease with a high prevalence, and using a test with a low specificity
c) Testing for a disease with a high prevalence, and using a test with a high specificity
Which of the following equations CORRECTLY describes negative predictive value?
a. True negative / (False negative + False negative)
b. True positive / (False negative + False positive)
c. True negative / (False negative + True negative)
d. True positive / (True positive + False positive)
c. True negative / (False negative + True negative)
Which of the following statements regarding statistical calculations is TRUE?
a. Negative predictive value is the probability that disease is present when the test is negative.
b. Positive predictive value is the probability that disease is not present when the test is negative
c. Sensitivity is the probability that a test result will be positive when the disease is present.
d. Specificity is the probability that a test result will be negative when the disease is present.
c. Sensitivity is the probability that a test result will be positive when the disease is present.
A new test is evaluated for the detection of Equine Viral Arteritis (EVA). 100 patients are evaluated that have similar clinical signs: 50 with the disease and 50 without.
If the sensitivity of the test is 80% and the specificity is 50%, how many patients show a NEGATIVE TEST?
a. 10
b. 25
c. 35
d. 50
c. 35
