Class 26-28: Screenings In medicine

Question 1

What’re 2 questions pt.’s should always ask their md’s?

Answer 1

How accurate is the screening test you’re recommending?

Based on test results, how confident will you be in your prediction of whether I do or don’t have the Dz?

Question 2

Sensitivity and specificity looks at which question?

Answer 2

How accurate is the screening test?

Question 3

4 screening outcomes:

Answer 3

True positive
True negative

False positive
False negative

Question 4

When someone w/ Dz is tested positive

Box A

Answer 4

True positive

Question 5

When someone w/o Dz is tested negative

Box D

Answer 5

True negative

Question 6

Rows on 2x2 table for medical screenings:

Answer 6

Positive
Negative

—instead of yes/no

Question 7

True positive is in which box for 2x2?

Answer 7

Box A

Question 8

True negative is in which box for 2x2?

Answer 8

Box D

Question 9

When someone w/ Dz is tested negative

Box C

Answer 9

False negative

Question 10

When someone w/o Dz tests positive

Answer 10

False positive

Question 11

False positive falls in which box of 2x2?

Answer 11

Box B

Question 12

False Negative is in which box for 2x2?

Answer 12

Box C

Question 13

How well a test can detect presence of Dz:

Answer 13

Sensitivity

Question 14

Positivity of test in the diseased

Rule out Dz

Answer 14

Sensitivity

Question 15

Looks at the % of true positives

Answer 15

Sensitivity

Question 16

Proportion of time that a test is POSITIVE in a patient that DOES have the Dz

Answer 16

Sensitivity

Question 17

If a test is either highly-sensitive that test is said to have a low:

Answer 17

A low false-negative rate

Question 18

How to calc sensitivity?

Answer 18

TP /
TP + FN

OR

TP /
All Dz

Question 19

How well a test can detect absence of disease when Dz is absent :

Answer 19

Specificity

Question 20

Negativity of test in the healthy

Rule out Dz

Answer 20

Specificity

Question 21

Proportion of time that a test is NEGATIVE in a pt. That does NOT have Dz

Answer 21

Specificity

Question 22

A highly specific test is said o have a low…

Answer 22

False positive rate

Question 23

Looks at % of time ppl w/o Dx get a negative test:

Answer 23

Specificity

Question 24

How to calc specificity:

Answer 24

TN /
TN + FP

OR

TN /
All not Dz

Question 25

Sensitivity is asso. W/ which box on 2x2?

Answer 25

Box A

Question 26

Specificity is asso. W/ which box on 2x2?

Answer 26

Box D

Question 27

Positive predictive value and negative predictive value answer which MD question?

Answer 27

How confident are you in test results?

Question 28

How accurately a positive test predicts the PRESENCE of Dz

Answer 28

PPV

Question 29

% of TP's in pt.'s w/ a positive test (correct prediction)

Answer 29

PPV Also called PVP-Predictive value-positive

Question 30

How to calc PPV?

Answer 30

TP / TP + FP OR TP / All positive tests

Question 31

PPV is asso. W/ which box on 2x2?

Answer 31

Box A

Question 32

NPV is asso. W/ which box on 2x2?

Answer 32

Box D

Question 33

How accurately a negative test predicts the ABSENCE of Dz

Answer 33

Negative predictive value | -NPV

Question 34

% of TN's in pt.'s w/ a negative test (correct prediction)

Answer 34

NPV Also, called PVN predictive value-negative

Question 35

How to calc NPV?

Answer 35

TN / TN + FN OR TN / All negative tests

Question 36

Proportion of time that a pt. Is correctly identified as either having a Dz or not having a Dz w/ a positive or negative test

Answer 36

Diagnostic accuracy (DA) or diagnostic precision (DP)

Question 37

How to calc DA?

Answer 37

TP (box A) + TN (box D) / all pt's

Question 38

Ratio of the probability of a given test result for a person w/ the Dz / probability of the same test result for a person w/o Dz Can be calc for both + and - results

Answer 38

Likelihood ratio (LR)

Question 39

Probability of a + test w/o Dz

Answer 39

LR+

Question 40

Probability of a - test w/ Dz / probability of a - test w/o Dz

Answer 40

LR-

Question 41

What should LR+ be if beneficial?

Answer 41

>10

Question 42

What should LR- be if beneficial ?

Answer 42

<0.1

Question 43

Ability to accurately discern btw those that DO and those that DONT have Dz

Answer 43

Validity

Question 44

Extent to which results accurately reflect what was being assessed

Answer 44

Internal validity

Question 45

Extent to which results are applicable to other populations Generalizability

Answer 45

External validity

Question 46

Ability of a test to give the same results on repeated uses Reproducibility

Answer 46

Reliability

Question 47

A valid test is always ______, yet a ______ test is not always ________

Answer 47

Reliable, reliable, valid

Question 48

Many diagnoses typically have 2 dichotomous outcomes (+,-)

Answer 48

Multiple cutoff values

Question 49

For screening test w. Numerical values, we use what for more efficient way to show a relationship btw sensitivity and specificity for tests w/ numerical outcomes?

Answer 49

ROCs Receiver operator curves