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BMS > Diagnostic Test Characteristics > Flashcards

Diagnostic Test Characteristics Flashcards

1
Q

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

A

Lyme disease

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2
Q

Caused by the bacterium Borrelia Burgdorferi

-transmitted through the bite of infected blacklegged ticks

A

Lyme disease

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3
Q

A serological test for lyme disease has a:

  1. ) Sensitivity of
  2. ) Specificity of
A
  1. ) 95%

2. ) 90%

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4
Q

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

A

Diagnostic testing

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5
Q

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

A

Gold standard

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6
Q

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

A

Accuracy, and what is a misclassification

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7
Q

What two aspects make up conditional probability?

A
  1. ) Sensitivity

2. ) Specificity

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8
Q

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

A

Sensitivity

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9
Q

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

A

Specificity

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10
Q

Diagnostic testing requires which three things?

A

Sensitivity, specificity, and prevalence

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11
Q

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

A

Prevalence

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12
Q

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

A

Prevalence

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13
Q

What are two other names for prevalence

A

Prior probability and pretest probability

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14
Q

The probability of having a disease given a positive test result

A

Positive Predictive value (“Predictive value positive)

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15
Q

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

A

Negative Predictive value of a test (“predictive value negative”)

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16
Q

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

A

Gold Standard

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17
Q

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

A

Nomogram

18
Q

Summarize both sensitivity and specificity into one number

A

Likelihood ratio

19
Q

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

A

LR+ = sensitivity / (1-specificity)

20
Q

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

A

LR- = (1-sensitivity) / Specificity

21
Q

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

A

Likelihood ratio

22
Q

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

A

Likelihood ratios

23
Q

To simplify likelihood ratios: values between 0 and 1

A

Decrease the probability of disease

24
Q

To simplify likelihood ratios: values greater than 1

A

Increase the probability of disease

25
Q

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

A

1

26
Q

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

A

Posttest odds = Pretest odds (prevalence) x LR

27
Q

What are odds?

A

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

28
Q

What is probability?

A

Probability = Odds / (1 + odds)

29
Q

What are the factors on predictive values?

A

Prevalence, specificity, sensitivity

30
Q

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

A

Predictive value

31
Q

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

A

Negative Predictive Value

32
Q

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

A

PPV

33
Q

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

A

NPV

34
Q

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

A

PPV

35
Q

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

A

False positives

36
Q

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

A

LR+

37
Q

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

A

LR-

38
Q

Will rarely miss people with the disease

A

Sensitive tests

39
Q

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

A

Specific tests

40
Q

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

A

Negative

41
Q

Most useful to confirm a diagnosis

-rarely gives false positives

A

Specific test

BMS (62 decks)

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