Diagnostic Tests 2

Question 1

name 3 limitations of predictive values

Answer 1

informative in generalities, often don’t have estimate of true prevalence, based on population so not readily applied to individuals, not easily translated from patient to patient

Question 2

define likelihood ratio

Answer 2

percent of diseased animals with a given test result, divided by precent of non-diseased animals with the same test result

Question 3

name 2 clinical limitations of likelihood ratios

Answer 3

few studies report test sensitivity and specificity in vet literature; studies may not be valid to your patient population; dependence on uncertain pretest probability

Question 4

name 3 reasons to use multiple diagnostic tests

Answer 4

improve overall diagnostic ability of diagnostic process; because tests are imperfect and therefore have limitations; combining complementary tests can increase certainty of disease status; be more efficient in use of diagnostic tests

Question 5

when applying two or more tests in a SERIES test, do ALL the tests need to be positive to get a positive result?

Answer 5

YES, ALL tests must be positive

Question 6

in regard to sensitivity and specificity, what is the objective of SERIES testing? what is the drawback?

Answer 6

SERIES testing objective is to increase diagnostic specificity (probability a non-diseased animal will be classified as negative). the diagnostic sensitivity is reduced.

Question 7

are SERIES tests more often performed as sequential tests or as simultaneous tests?

Answer 7

SERIES tests are often performed as SEQUENTIAL tests (one after the other)

Question 8

when applying two or more tests in a PARALLEL test, do ALL the tests need to be positive to get a positive result?

Answer 8

NO, considered positive if ANY single test is positive

Question 9

are PARALLEL tests more often performed as sequential tests or as simultaneous tests?

Answer 9

PARALLEL tests are more often performed as SIMULTANEOUS tests (at the same time)

Question 10

in regard to sensitivity and specificity, what is the objective of PARALLEL testing? what is the drawback?

Answer 10

PARALLEL testing objective is to increase diagnostic sensitivity (probability a diseased animal will be categorized as positive). drawback is reduced diagnostic specificity

Question 11

you wish to confirm that a band has cowbell fever. should you use series testing or parallel testing?

Answer 11

Series testing. want to rule in disease (high specificity, want low risk of false positives)

Question 12

you want to be as confident as possible that your animals are free from disease. should you use series or parallel testing?

Answer 12

parallel testing (want high sensitivity, low risk of false negatives)