module 2

Question 1

what do we mean when we ask if the diagnostic tests are accurate

Answer 1

does the diagnostic test provide sufficient information to reliably distinguish individuals with or without the condition of interest

how much does the probablity change pre and post test

Question 2

are diagnostic clinical test ever 100% accurate

Answer 2

no

• there is alway a chance of false negatives and positives

Question 3

what does sensitivity address

Answer 3

how good in the test ID people with the disease

snOUT - rule out

Question 4

what does specificity addres

Answer 4

how good is the test at ID without the disease

spIN

Question 5

what does the positive predictor rule address

Answer 5

if a person test positive - what is the probability that they have the condition

ID those who have the disease amongst those who tested positive

Question 6

what does the negative predictor rule address

Answer 6

if a person test neg, what is the prob that they do not have the condition

ID those who do not have the disease among those who have a neg test result

Question 7

positive LR addresses

Answer 7

how much more likely is a positive test found in someone with the disease than in someone without it

Question 8

negative LR addresses

Answer 8

how much more likely is a neg found in someone without the disease compare to someone who has it

Question 9

is sensitivity a true positive or true negative rate

Answer 9

true positive

test with high sensitivity have few false negatives

therefore neg result rule out the condition

Question 10

is specificity a true positive or true negative rate

Answer 10

true negative

have few false positives so if you have a positive it rules in the conditions

Question 11

false positives impact spin or snout

Answer 11

spin

Question 12

false negative impact spin or snout

Answer 12

snout

Question 13

what is the difference between sn/sp and PPV/NPV - sn/sp

Answer 13

calculated from those who have the disease and those who do not

stable regardless of the disease prevelence in different populations

Question 14

what is the difference between sn/sp and PPV/NPV - PPV/NPV

Answer 14

calculated from those who are positive and those who are negative

influence by disease prevelance

Question 15

pre test and post test sn/sp

Answer 15

sn/sp do not provide us information on shift from pre and post test

Question 16

LR and pre and post test

Answer 16

these can tell about the shift pre and post test

qualifies the shift from pre and post test

Question 17

what does LR examine

Answer 17

how likely the disease is given a positive or negative test result

Question 18

postive LR - what does it tell us

Answer 18

given a positive test, are the odds the odds of having the condition larger

expresses the change in odds favoring the condition during a positive test

Question 19

negative LR - what does it tell us

Answer 19

express the changes in odds favoring the codition given a neg result

given a neg result, are the odds of the condition smaller

Question 20

what is pre test probality

Answer 20

what we know before applying the diagnostic test

clinician best guess

Question 21

post test probability

Answer 21

what we know after applying the DTI

can be quatified by using LR

Question 22

large positive LR indicates what

Answer 22

the condition is more likely

Question 23

small negative LR indicates what

Answer 23

the condition is less likely

Question 24

high specificity and +LR

Answer 24

larger + LR

due to the low false positive rate

Question 25

high sensitivity and -LR

Answer 25

small -LR rate

due to low false negative

Question 26

how can we tell the precision of the diagnostic accuracy esitmates

Answer 26

CI
- do not want to cross 0

Question 27

if you have a larger CI is your information precise

Answer 27

no

Question 28

over all what is the reason why we use LR

Answer 28

show the change in probability pre and post test

Question 29

how do you know if a diagnostic test is reliable, accurate, and precise

Answer 29

is the test reproducible - good intra and inter rater reliablity

how accurate is the test (sn, sp, LR)

Question 30

Intrarater reliability

Answer 30

how consistent an individual is at measuring a constant phenomenon

Question 31

interrater reliability

Answer 31

how consistent different individuals are at measuring the same phenomenon

Question 32

what % of sp or sn is good

Answer 32

80

Question 33

sp + sn test to avoid

Answer 33

do not equal at least 100

Question 34

what is youdans index

Answer 34

showing the diagnostic perfromance of a test
sn + sp - 1 >.5 (ideally 1)

Question 35

what is a reciever operant curve

Answer 35

used when there is an overlap between those with or without a presentation

graphic method to calculate sn and sp when a range of test scores are bing considered

Question 36

what is an ROC used for

Answer 36

determine the optimal cut value between healthy and disease states

determine the MCID

Question 37

what is plotted on ROC’s

Answer 37

true positive rate vs false positive rate

Question 38

where is the optimal threshold value found in ROC

Answer 38

in the point closest to the upper left corner

Question 39

what does the area under thee curve depend on

Answer 39

the true positive rate

Question 40

a large area under the curve tells us what

Answer 40

better diagnostic accuracy

Question 41

what happens if the AUC is a flat line

Answer 41

this is a worthless test
AUC = .5