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BSP Exam II > Screenings in Medicine > Flashcards

Screenings in Medicine Flashcards

1
Q

In a 2x2 table for screening tests, what are the labels for the rows and columns?

A

Rows: screening test pos/neg
Columns: disease presence “truth”

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2
Q

What is a “true positive”? What box in a 2x2 table do these people live in?

A

Someone has the disease and the screening test comes back positive. Test is accurate so it is a “true” measure. Live in box “A”

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3
Q

What is a “true negative”? What box of the 2x2 table do these people live in?

A

Someone who doesn’t have the disease and the screening test comes back negative. The test is accurate so it is a “true” measure. Live in box “D”

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4
Q

What is a “false negative”? What box of the 2x2 table do these people live in?

A

When the screening test comes back negative when the person actually does have the disease. The test is not accurate. Live in box “C”

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5
Q

What is a “false positive”? What box of the 2x2 table do these people live in?

A

When the screening test comes back positive when the patient does not actually have the disease. The test is not accurate. Live in box “B”

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6
Q

What is the sensitivity of a screening test?

A

How well a test can detect the presence of disease when in fact disease IS present.
Proportion of time that a test is positive in a patient that does have disease.

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7
Q

If you have a highly sensitive screening test, what is the rate of false negatives?

A

Very low

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8
Q

How would you calculate the sensitivity of a screening test?

A

Sensitivity= TP/(all diseased)x100%

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9
Q

When measuring the sensitivity of a screening test, would you be analyzing rows or columns?

A

Columns

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10
Q

What is the specificity of screening tests?

A

How well a test can detect absence of disease when in fact the disease is absent.
Proportion of time that a test is negative in a patient that does NOT have the disease

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11
Q

A highly specific screening test has what kind of rate of false positives?

A

Very low

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12
Q

How would you measure the specificity of a screening test?

A

Specificity=TN/(all not diseased)x100%

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13
Q

What is the positive predictive value of a screening test?

A

How accurately a positive test predicts the presence of disease.
Measures the percentage of TP’s in patients with a positive test (correct predilection)

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14
Q

When measuring specificity of a screening test, are you considering the rows or columns of the 2x2 table?

A

Columns

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15
Q

How would you calculate the positive predictive value of a screening test?

A

PPV=TP/(all positive tests)x100%

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16
Q

When considering the positive predictive value of a screening test, are you looking at the rows or columns of a 2x2 box?

A

Rows

17
Q

What is the negative predictive value of a screening test?

A

How accurately a negative test predicts the absence of disease.
Percentage of TN’s in patients with a negative test (correct prediction)

18
Q

How would you calculate the negative predictive value or a screening test?

A

NPV=TN/(all negative tests)x100%

19
Q

When considering the negative predictive value of a screening test, are you looking at the rows or columns of a 2x2 box?

A

Rows

20
Q

What is the diagnostic accuracy (DA) or diagnostic precision (DP) of a screening test?

A

Proportion of the time that a patient is correctly identified as either having a disease or not having a disease with a positive or negative test, respectively

21
Q

How would you calculate the diagnostic accuracy (DA) or diagnostic precision (DP) for a screening test?

A

DA/DP=(TP+TN)/(all patients)x100%

22
Q

When considering the diagnostic accuracy (precision) of a screening test, are you looking at the rows or columns of a 2x2 box?

A

Neither, it measures A+B/ total

23
Q

What is a likelihood ratio of a screening test measuring?

A

Ratio of probability of a given test results (pos or neg) for a person WITH the disease / probability of the same test result (pos or neg) for a person WITHOUT the disease

24
Q

What is the likelihood ratio positive (LR+) in a screening test?

A

Probability of a positive test in the presence of disease / probability of a positive test in the absence of disease

25
Q

What is the likelihood ratio negative (LR-) in a screening test?

A

Probability of a negative test in the presence of disease / probability of a negative test in the absence of disease

26
Q

What are the 2 ways you can calculate the likelihood ratio positive of a screening test?

A
  1. Sensitivity / (1-specificity)

2. [(A/(A+C))/(B/(B+D))]

27
Q

What are the two ways you can calculate the likelihood ratio negative of a screening test?

A
  1. (1-Sensitivity) / Specificity

2. [(C/(A+C))/(D/(B+D))]

28
Q

What should the result of a calculation for LR+ and LR- be to demonstrate that the tests are most beneficial?

A

LR+ should be >10

LR- should be <0.1

29
Q

What is validity and what are the two types of validity?

A
  • Ability to accurately discern between those that do and those that do not have the disease
  • Internal and external validity
30
Q

What is internal validity?

A

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

31
Q

What is external validity?

A

Extent to which results are applicable to other populations (not included in the original study; aka generalizability)

32
Q

What is reliability?

A

Ability of a test to give the same result on repeated uses

***reproducibility/consistency

33
Q

Since a valid test is always reliable, is a reliable test always valid?

A

NO, a bad test can be reproducible without being accurate

34
Q

What is used when a screening test has multiple cutoff values? Why?

A

ROCs (receiver operator curves)
More efficient way to show a relationship between sensitivity and specificity for tests with numerical (continuous) outcomes

BSP Exam II (10 decks)

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