Classes 26-28 Screenings in Medicine Flashcards Preview

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Flashcards in Classes 26-28 Screenings in Medicine Deck (24)
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1

True Positive (TP)

Test correctly reports a positive result in a patient that actually does have the disease
(Box A)

2

True Negative (TN)

Test correctly reports a negative result in a patient that actually does not have the disease
(Box D)

3

False Positive (FP)

Test incorrectly reports a positive result in a patient that actually does not have the disease
(Box B)

4

False Negative (FN)

Test incorrectly reports a negative result in a patient that actually does have the disease
(Box C)

5

Sensitivity

How well a test can detect presence of disease when in fact disease is present -- Positivity-of-test in the diseased
Proportion of time that a TEST is positive in a patient that does have the disease

6

Sensitivity equation

Sensitivity = TP/(TP + FN) x 100%
Sensitivity = TP/(all Diseased) x 100%

7

A highly sensitive test has:

A low false negative rate

8

Specificity

How well a test can detect absence of disease when in fact the disease is absent -- Negativity-of-test in the healthy
Proportion of time that a TEST is negative in a patient that does not have the disease

9

Equation for Specificity

Specificity = TN/(TN + FP) x 100%
Specificity = TN/(All not diseased) x 100%

10

A highly specific test has:

A low false positive rate

11

Positive Predictive Value (PPV)

How accurately a positive test predicts the presence of disease
Percentage of TP's in patients with a positive test (correct prediction)
Also referred to a predictive value-positive (PVP)

12

Equation for PPV

PPV = TP/(TP + FP) x 100%
PPV = TP/(All Positive Tests) x 100%

13

Negative Predictive Value (NPV)

How accurately a negative test predicts the absence of disease
Percentage of TN's in patients with a negative test (correct prediction)
Also referred to as Predictive Value-Negative (PVN)

14

Equation for NPV

NPV = TN/(TN + FN) x 100%
NPV = TN/(All Negative Tests) x 100%

15

Diagnostic Accuracy (DA) or Diagnostic Precision (DP)

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

16

Calculation for DA (or DP)

= (TP/TN) / (TP + FP + FN + TN) x 100%
= (TP/TN) / (All patients) x 100%

17

Likelihood Ratio (LR)

Probability of a given test result (positive or negative) for a person with the disease / probability of the same test result (+ or -) for a person without the disease

18

Likelihood Ratio Positive (LR+)

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

19

Equation for Likelihood Ratio Positive (LR+)

[(A/(A+C)) / (B/(B+C))]
Sensitivity/(1-Specificity)

20

Likelihood Ratio Negative (LR-)

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

21

Equation for Likelihood Ratio Negative (LR-)

[(C/(A+C)) / (D/(B+D))]
(1-Sensitivity) / Specificity

22

LR+ should be _____ to demonstrate the test is most beneficial.

>10

23

LR- should be _____ to demonstrate the test is most beneficial

24

ROC (Receiver Operator Curves)

A more efficient way to show a relationship between sensitivity & specificity for tests with numerical (continuous) outcomes