Screenings in Medicine

Question 1

What are the two questions that a patient should ask the physician when a medical screening is recommended?

Answer 1

1. how accurate the screening test is

2/ How confident the doc is about the prediction of the disease

Question 2

What are the 4 outcomes to a screening?

Answer 2

true positive
false positive
true negative
false negative

Question 3

Define true positive

Answer 3

the test correctly reports a positive test result in a patient that actually has the disease

Question 4

Define True negative

Answer 4

the test correctly reports a negative test result in a patient that does not have the disease

Question 5

Which portion of the 2X2 table does a true positive fall under?

Answer 5

A

Question 6

What portion of the 2X2 table does a true negative fall under?

Answer 6

D

Question 7

Define False positive

Answer 7

A test incorrectly reports a positive result in a patient that does not have the disease

Question 8

Define a False Negative

Answer 8

A test incorrectly reports a negative test result in a patient that does have the disease

Question 9

Which portion of the 2X2 table does the false positive fall under?

Answer 9

B

Question 10

Which portion of the 2X2 table does the false negative fall under?

Answer 10

C

Question 11

What are the two aspects that describes the accuracy of the screening test?

Answer 11

Sensitivity and Specificity

Question 12

Define sensitivity

Answer 12

How well a test can detect the presence of disease wen the disease is present

Question 13

What is the equation for sensitivity?

Answer 13

TP/(TP+FN) X 100% LOOK AT ALL DISEASED

Question 14

Define Specificity

Answer 14

How well a test can detect the absence of disease when in fact the disease is absent

Question 15

What is the equation for specificity?

Answer 15

TN/TN+FP X 100% (ALL NOT DISEASED)

Question 16

What are the two elements that represent the doctors confidence?

Answer 16

Positive predictive value and negative predictive value

Question 17

Define positive predictive value

Answer 17

How accurately a positive test predicts the presence of disease

Question 18

What is the equation of positive predictive value?

Answer 18

PVV= TP/ (TP+FP) x 100% (ALL POSITIVE TESTS)

Question 19

Define negative predictive value

Answer 19

How accurately a negative test predicts the absence of disease

Question 20

What is the equation for the negative predictive value

Answer 20

NPV=TN/(TN+FN) x 100%

Question 21

What happens to the PPV as the prevalence gets closer to 100%?

Answer 21

It sky rockets to 100% as well

WHY? because tests will increase with more disease

Question 22

Will sensitivity and specificity change as the prevalence gets closer to 100%?

Answer 22

No they will not because the TEST DOES NOT CHANGE

Question 23

Define diagnostic accuracy

Answer 23

the proportion of total screenings that a patient is correctly identified as either having a disease (TP) or not having a disease (TN) with either a positive or a negative test, respectively

Question 24

What is the equation for diagnostic accuracy?

Answer 24

(TP+TN)/ (TP+FN+FP+TN)

Question 25

Define the likelihood ratio.

Answer 25

the ratio of the probability of a given test result for a person with disease OVER the probability of the same test result for a person WITHOUT the disease

Question 26

What is in the numerator for the likelihood ratio?

Answer 26

the people with disease

Question 27

Define the likelihood ratio positive

Answer 27

The probability of a positive test in the presence of disease over the probability of a positive test in the absence of disease

Question 28

Using the letters from the 2X2 table, what is the equation for the likelihood ratio positive?

Answer 28

(A/A+C)/(B/B+D)

Question 29

Define the likelihood ratio negative

Answer 29

The probability of a negative test in the presence of disease over the probability of a negative test in the absence of disease

Question 30

Using the letters from the 2X2 table, what is the equation for the likelihood ratio negative?

Answer 30

(C/A+C)/(D/B+D)

Question 31

For a test to be deemed beneficial, what does the LR+ have to be?

Answer 31

More than 10

Question 32

For a test to be deemed beneficial, what does the LR-have to be?

Answer 32

Less than 0.1

Question 33

Define validity

Answer 33

the ability to accurately discern between those that do and those that do not have the disease analogous to precision

Question 34

Define internal validity

Answer 34

the extent to which results accurately reflect what was being assessed (true situation of study population)

Question 35

Define External validity

Answer 35

the extent to which the results are applicable to other populations included in the original study Generalizability

Question 36

Define reliability

Answer 36

the ability of a test to give the same result on repeated uses analogous to reproducibility/consistency

Question 37

Is a valid test always reliable?

Answer 37

Yes

Question 38

Is a reliable test always valid

Answer 38

NAH