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Epidemiology Exam 2 > Screenings in Medicine > Flashcards

Screenings in Medicine Flashcards

1
Q

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

A
  1. how accurate the screening test is

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

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2
Q

What are the 4 outcomes to a screening?

A

true positive
false positive
true negative
false negative

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3
Q

Define true positive

A

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

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4
Q

Define True negative

A

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

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5
Q

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

A

A

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6
Q

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

A

D

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7
Q

Define False positive

A

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

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8
Q

Define a False Negative

A

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

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9
Q

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

A

B

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10
Q

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

A

C

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11
Q

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

A

Sensitivity and Specificity

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12
Q

Define sensitivity

A

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

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13
Q

What is the equation for sensitivity?

A

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

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14
Q

Define Specificity

A

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

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15
Q

What is the equation for specificity?

A

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

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16
Q

What are the two elements that represent the doctors confidence?

A

Positive predictive value and negative predictive value

17
Q

Define positive predictive value

A

How accurately a positive test predicts the presence of disease

18
Q

What is the equation of positive predictive value?

A

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

19
Q

Define negative predictive value

A

How accurately a negative test predicts the absence of disease

20
Q

What is the equation for the negative predictive value

A

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

21
Q

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

A

It sky rockets to 100% as well

WHY? because tests will increase with more disease

22
Q

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

A

No they will not because the TEST DOES NOT CHANGE

23
Q

Define diagnostic accuracy

A

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

24
Q

What is the equation for diagnostic accuracy?

A

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

25
Q

Define the likelihood ratio.

A

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

26
Q

What is in the numerator for the likelihood ratio?

A

the people with disease

27
Q

Define the likelihood ratio positive

A

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

28
Q

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

A

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

29
Q

Define the likelihood ratio negative

A

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

30
Q

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

A

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

31
Q

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

A

More than 10

32
Q

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

A

Less than 0.1

33
Q

Define validity

A

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

34
Q

Define internal validity

A

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

35
Q

Define External validity

A

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

36
Q

Define reliability

A

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

37
Q

Is a valid test always reliable?

38
Q

Is a reliable test always valid

Epidemiology Exam 2 (6 decks)

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