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