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MIDS 199 > Ch 7b Sensitivity + Specificity > Flashcards

Ch 7b Sensitivity + Specificity Flashcards

1
Q

What is FNV?

A

-False negative value
-The # of diseased persons testing negative

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2
Q

What is FPV?

A

-False positive value
-The # of non-diseased persons who tested positive

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3
Q

What is TD?

A

Total # of diseased persons

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4
Q

What is TN?

A

Total # of persons testing negative

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5
Q

What is TND?

A

Total # of non-diseased persons

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6
Q

What is TNV?

A

-True negative value
-The # of disease free persons testing negative

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7
Q

What is TOT?

A

Total # of persons in the study

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8
Q

What is TP?

A

Total # of persons testing positive

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9
Q

What is TPV?

A

-True positive value
-The # of diseased persons testing positive

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10
Q

Is the sensitivity for scrotal + OB exams high or low?

A

High - b/c u/s is the gold standard

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11
Q

If the test result is positive: list the correct definitions for the disease, non-diseased + total?

A

Disease: TPV (true positive value)
Non-diseased: FPV (false positive value)
Total: TP (total positive people)

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12
Q

If the test result is negative: list the correct definitions for the disease, non-diseased + total?

A

Disease: FNV (false negative value)
Non-diseased: TNV (true negative value)
Total: TN (total negative people)

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13
Q

List the total test results: list the correct definitions for the disease, non-diseased + total?

A

Disease: TD (total diseased people)
Non-diseased: TND (total non-diseased people)
Total: TOT (total people in study)

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14
Q

List the sensitivity formula?

A

SENS = TPV/TD

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15
Q

Define sensitivity?

A

-True positive rate
-The sensitivity of a test is the proportion of people with the disease who will have a positive result

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16
Q

A highly sensitive test is one that correctly identifies what?

A

Patients with a disease

17
Q

A test that is 100% sensitive will identify what?

A

All patients who have the disease

18
Q

List the specificity formula?

A

SPEC = TNV/TND

19
Q

Define specificity?

A

-True negative rate
-The specificity of a test is the proportion of people without the disease who will have a negative result

20
Q

The specificity of a test refers to how well a test identifies what?

A

Pt’s who do not have a disease

21
Q

A test that has 100% specificity will identify what?

A

100% of pt’s who do not have the disease

22
Q

Do high sensitivity tests have high or low specificity?

A

Low

(think they are inverse of each other)

23
Q

High sensitivity + low specificity is good for catching actual cases of the disease. Do they have a high or low rate of false positives?

A

High false positive rate

(going to call pt’s back for more testing than they need to. A biopsy should be done)

24
Q

Give an example of a test that generally has a high sensitivity (70-80%) + low specificity?

A

Mammograms

(sensitivity depends on tumor size, pt age, etc)

25
Q

High specificity + low sensitivity has a high or low rate of false negatives?

A

Higher false negative rate (misses true positives)

(bad at telling us if a person has the disease, must do other tests to check)

26
Q

Give an example of a test that has low sensitivity (27%) + high specificity (94%)?

A

Nitrate dipstick test - used to test for urinary tract infections (UTIs) in hospitalized pt’s

27
Q

List the positive predictive value formula?

A

PPV = TPV/TP

28
Q

What is the PPV?

A

-Positive predictive value
-Is the probability that a positive result in a hypothesis test means that there is a real effect
-Is the probability of pt’s who have a positive test result to actually have the disease

29
Q

Positive predictive values are influenced by what?

A

How common the disease is in the population being tested

(ex. if the disease is very common than a person with a positive test result is more likely to actually have the disease, opposed to a person with a positive test result in a population where the disease is rare)

30
Q

List the negative predictive value formula?

A

NPV = TNV/TN

31
Q

What is the NPV?

A

-Negative predictive value
-The probability that people who get a negative test result truly do not have the disease
-The probability that a negative test result is accurate

32
Q

Give an example of a test that we would want to have a high negative predictive value?

A

Covid tests - we want a high NPV so we know for sure we do not have covid + do not isolate for no reason

33
Q

List the accuracy of a test formula?

A

ACC = (TPV + TNV)/TOT

34
Q

What is ACC?

A

-Accuracy of a test
-Is the proportion of all tests in the study (TOT) that have the correct result

MIDS 199 (15 decks)

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