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Flashcards in Diagnostic Test Characteristics Deck (41):
1

Indicated by fever, headache, fatigue, and a characteristic skin rash (erythema migrans)

Lyme disease

2

Caused by the bacterium Borrelia Burgdorferi

-transmitted through the bite of infected blacklegged ticks

Lyme disease

3

A serological test for lyme disease has a:
1.) Sensitivity of
2.) Specificity of

1.) 95%
2.) 90%

4

A form of testing based on test results that predicts the disease status

Diagnostic testing

5

To develop a diagnostic test, you want to compare it to a current

Gold standard

6

To develop a diagnostic test, you want to define the test results, meaning what is the

Accuracy, and what is a misclassification

7

What two aspects make up conditional probability?

1.) Sensitivity
2.) Specificity

8

The probability of testing positive, given that a patient has a disease

Sensitivity

9

The probability of testing negative, given that a patient does not have the disease

Specificity

10

Diagnostic testing requires which three things?

Sensitivity, specificity, and prevalence

11

The proportion of a group of people possessing a clinical condition or outcome at a given point in time

Prevalence

12

Can be thought of as the probability of disease before the test result is known

Prevalence

13

What are two other names for prevalence

Prior probability and pretest probability

14

The probability of having a disease given a positive test result

Positive Predictive value ("Predictive value positive)

15

The probability of not having a disease, given a negative test result

Negative Predictive value of a test ("predictive value negative")

16

A diagnostic test's accuracy is determined by comparing it to a

Gold Standard

17

Comes from the pretest probability and likelihood ratio and is used to derive the posttest probability

Nomogram

18

Summarize both sensitivity and specificity into one number

Likelihood ratio

19

How do we find the positive likelihood ratio (LR+)?

LR+ = sensitivity / (1-specificity)

20

How do we find the negative likelihood ratio (LR-)?

LR- = (1-sensitivity) / Specificity

21

Defined as the probability of that test result in people with the disease divided by the probability of the result in people without the disease

Likelihood ratio

22

Express how many times more (or less) likely a test result is to be found in diseased, compared with non-diseased, people

Likelihood ratios

23

To simplify likelihood ratios: values between 0 and 1

Decrease the probability of disease

24

To simplify likelihood ratios: values greater than 1

Increase the probability of disease

25

The probability of disease is not affected if the likelihood ratio is

1

26

How do we use the likelihood ratio to calculate the post test odds?

Posttest odds = Pretest odds (prevalence) x LR

27

What are odds?

Odds = probability of event / (1- probability of event)

28

What is probability?

Probability = Odds / (1 + odds)

29

What are the factors on predictive values?

Prevalence, specificity, sensitivity

30

The probability of disease, given the results of a test is called the

Predictive value

31

The more sensitive a test is, the better will be it's

Negative Predictive Value

32

The more specific the test is, the better will be its

PPV

33

Assesses how confident the clinician can be that a negative test rules out the disease being sought

NPV

34

Assesses how confident the clinician can be that a positive test confirms the diagnosis

PPV

35

Positive results, even for a very specific test, when applied to patients with a low likelihood of having the disease will largely be

False positives

36

The ratio of the proportion of diseased people with a positive test result to the proportion of nondiseased people with a positive result

LR+

37

The ratio of the proportion of diseased people with a negative test result divided by the proportion of non-diseased people with a negative test result

LR-

38

Will rarely miss people with the disease

Sensitive tests

39

Will rarely misclassify people as having the disease when they do not

Specific tests

40

A highly sensitive test is most helpful to the clinician when the test result is

Negative

41

Most useful to confirm a diagnosis

-rarely gives false positives

Specific test

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