Diagnostic Test Characteristics

Question 1

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

Answer 1

Lyme disease

Question 2

Caused by the bacterium Borrelia Burgdorferi

-transmitted through the bite of infected blacklegged ticks

Answer 2

Lyme disease

Question 3

A serological test for lyme disease has a:

1. ) Sensitivity of
2. ) Specificity of

Answer 3

1. ) 95%

2. ) 90%

Question 4

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

Answer 4

Diagnostic testing

Question 5

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

Answer 5

Gold standard

Question 6

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

Answer 6

Accuracy, and what is a misclassification

Question 7

What two aspects make up conditional probability?

Answer 7

1. ) Sensitivity

2. ) Specificity

Question 8

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

Answer 8

Sensitivity

Question 9

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

Answer 9

Specificity

Question 10

Diagnostic testing requires which three things?

Answer 10

Sensitivity, specificity, and prevalence

Question 11

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

Answer 11

Prevalence

Question 12

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

Answer 12

Prevalence

Question 13

What are two other names for prevalence

Answer 13

Prior probability and pretest probability

Question 14

The probability of having a disease given a positive test result

Answer 14

Positive Predictive value (“Predictive value positive)

Question 15

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

Answer 15

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

Question 16

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

Answer 16

Gold Standard

Question 17

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

Answer 17

Nomogram

Question 18

Summarize both sensitivity and specificity into one number

Answer 18

Likelihood ratio

Question 19

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

Answer 19

LR+ = sensitivity / (1-specificity)

Question 20

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

Answer 20

LR- = (1-sensitivity) / Specificity

Question 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

Answer 21

Likelihood ratio

Question 22

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

Answer 22

Likelihood ratios

Question 23

To simplify likelihood ratios: values between 0 and 1

Answer 23

Decrease the probability of disease

Question 24

To simplify likelihood ratios: values greater than 1

Answer 24

Increase the probability of disease

Question 25

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

Answer 25

1

Question 26

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

Answer 26

Posttest odds = Pretest odds (prevalence) x LR

Question 27

What are odds?

Answer 27

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

Question 28

What is probability?

Answer 28

Probability = Odds / (1 + odds)

Question 29

What are the factors on predictive values?

Answer 29

Prevalence, specificity, sensitivity

Question 30

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

Answer 30

Predictive value

Question 31

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

Answer 31

Negative Predictive Value

Question 32

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

Answer 32

PPV

Question 33

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

Answer 33

NPV

Question 34

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

Answer 34

PPV

Question 35

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

Answer 35

False positives

Question 36

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

Answer 36

LR+

Question 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

Answer 37

LR-

Question 38

Will rarely miss people with the disease

Answer 38

Sensitive tests

Question 39

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

Answer 39

Specific tests

Question 40

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

Answer 40

Negative

Question 41

Most useful to confirm a diagnosis -rarely gives false positives

Answer 41

Specific test