Lecture 10 (Diagnosis) Flashcards

1
Q

Sensitivity equation and table:

A

TP/(TP+FN)

SNOUT

2
Q

A sensitive test should be chosen when:

A
• there is an important penalty for missing the diagnosis.
• very few false negatives
3
Q

A specific test should be utilized when:

A
• false-positive can harm the patient physically, emotionally, or financially.
• used to “rule-in” diagnoses when data suggest.
• very few false positives
4
Q

Specificity equation and table:

A

TN/(TN+FP)

SPIN

5
Q

A sensitive tests yields:

A
• very few false negatives
• a lot of false positives
• SNOUT
6
Q

A specific test yields very few:

A

false positives

SPIN

7
Q

Positive predictive value:

A
• if test is positive, how likely it is a TP
• depends on sensitivity, specificity, and prevalence
• decreases as prevalence decreases
8
Q

Positive predictive value equation and table:

A

TP/(TP+FP)

9
Q

+PV depends on:

A
1. sensitivity
2. specificity
3. prevalence
10
Q

+PV decreases as:

A

prevalence decreases

11
Q

Negative predictive value:

A
• if test is negative, how likely it is TN
12
Q

Negative predictive value equation and table:

A

TN(TN+FN)

13
Q

False positive rate =

A

1 - specificity

14
Q

ROC Curves:

A
• plots sensitivity versus specificity
• closer you are to the upper left hand corner of the graph, the better the test is.
15
Q

Pre-test probability =

A

prevalence

16
Q

Posterior (post-test) probabilities are:

A
• the probability of disease after the test result is known
• likelihood ratios can be used to calculate probability of disease after a positive or negative test.
17
Q

Likelihood ratios:

A
• used to calculate probability of disease after a positive or negative test.
• ​tells you how many times more likely a test result is to be found in people with disease compared to people without disease
18
Q

Positive Likelihood Ratio equation:

A

LR+ = Sn / (1-Sp)

19
Q

Negative Likelihood Ratio equation:

A

LR- = (1-Sn) / Sp

20
Q

How to use a nomogram:

A
• Place straightedge at correct prevalence and likelihood values to get the post-test probability.
21
Q

Parallel testing:

A
• Test A or Test B or Test C must be positive
• if any one test is positive, the result is positive.
• high sensitivity
22
Q

Serial testing:

A
• Test A and Test B and Test C all must be positive
• if all tests positive, result is positive
• high specificity