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Flashcards in Diagnostic Tests Deck (52)
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1

diagnosis

classify animals as having a disease (or other health related state) or not

2

uses of diagnostic tests

clinical medicine: treatment and prognosis

surveillance: identify changes in disease status

international trade: keep infected animals out

research: identify and monitor research subjects

3

Dichotomous tests

only 2 possible answers

positive or negative

e.g radiographs, MRI, PM

4

continuous tests

continuum of possible answers, still need to classify as positive or negative

e.g serum chemistry, antibody titers, CBC

5

hematology diagnostic tests

measures amount of different cell types in a venous blood sample

6

biochemical diagnostic tests

measures enzymes, metabolites, proteins, etc-usually in venous blood sample

7

immunological diagnostic tests

use antigen to measure antibodies or vice versa

8

example of immunologic tests

SNAP FIV/FeLV

9

pathogen detection tests

detects the pathogen itself (or specific parts of it)

ex: microscopy, culture, virus isolation, PCR

10

T/F some test for epidemiological investigations "fingerprint" pathogens or discriminate infected from vaccinated animals (DIVA)

true

11

T/F usually cant measure the disease itself

true

12

what is measured?

'something' (chemical, antigen, etc) that is present in a certain quantity when an animal has a certain disease/underlying pathogen

test value

13

how do diagnostic tests work?

sample taken --> test is run and test value is produced --> decision i (+/-) is made by test or diagnostician (test result)

14

cut off value

determine experimentally as the value that minimizes false positive/ false negative results

15

T/F usually there is a clear separation in the test values between diseased and non diseased

false

16

T/F some non-diseased animals may have higher test values than some of the disease and vice versa

true

17

T/F can have false positives/negatives

true

18

True positive

diseased animal that tests positive

19

true negative

non-diseased animal that tests negative

20

false negative

diseased animal that test negative

21

false positive

non-diseased animal that tests positive

22

how are gold standard tests used

true disease status of individuals is often determined using a gold standard test, against which the performance of a new test is evaluated

23

disadvantages of gold standard test

labor intensive, impractical, highly invasive, slow and/or expensive

24

every test is evaluated by how accurately it classifies:

diseased individuals as test positive

non-diseased individuals as test negative

25

how to evaluate a test

test group of disease animals

test a group of non-diseased animals

establish a cut-off value

26

what are the 2 parameters to evaluate diagnostic test

sensitivity (Se)

Specificity (Sp)

27

diseased animals are used to determine

sensitivity (of the new test)

28

non diseased animals are used to determine

specificity (of the new test)

29

T/F Se and Sp are proportions

true

30

determining sensitivity

test a group of diseased animals

proportion of diseased animals that the test correctly classifies as positive