Screenings in Medicine

Question 1

What are the 2 questions that patients should ask their physician when a medical screening is recommended?

Answer 1

• How accurate is the screening test?

- How confident will you be in your prediction?

Question 2

True Positive (TP)

Answer 2

Test correctly reports positive result in a patient that actually does have the disease

Question 3

True Negative (TN)

Answer 3

Test correctly reports a positive result in a patient that actually does not have the disease

Question 4

False Positive (FP)

Answer 4

Test incorrectly reports a positive result in a patient that actually does not have the disease

Question 5

False Negative (FP)

Answer 5

Test incorrectly reports negative result in a patient that actually does have the disease

Question 6

Sensitivity Definition

Answer 6

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

Question 7

Sensitivity Equation

Answer 7

Sensitivity = TP / (TP + FN) x 100

= TP / all diseased x 100

Question 8

Specificity Definition

Answer 8

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

Question 9

Specificity Equation

Answer 9

Specificity = TN/ (TN + FP) x 100

= TN / all not diseased x 100

Question 10

Positive Predictive Value Definition

Answer 10

How accurately a positive test predicts the presence of disease

Question 11

Positive Predictive Value (PPV) Equation

Answer 11

PPV = TP/ (TP + FP) x 100

= TP / all positive tests x 100

Question 12

Negative Predictive Value (NPV) Definition

Answer 12

How accurately a negative test predicts the absence of disease

Question 13

NPV Equation

Answer 13

NPV = TN / (TN + FN) x 100

= TN / all negative tests x 100

Question 14

Diagnostic Accuracy (DA) or Diagnostic Precision (DP) Definition

Answer 14

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

Question 15

DA or DP Equation

Answer 15

DA/DP = (TP + TN) / ( TP + FP + FN + TN) x 100

= (TP + TN) / All patients X 100

Question 16

Likelihood Ratio Positive

Answer 16

Probability of positive test with disease / probability of positive test without disease

• [A/A+C] / [B/B+D]

Question 17

Likelihood Ratio Negative

Answer 17

Probability of negative test with disease / probability of negative test without disease

[C/A+C] / [D/B+D]

Question 18

Validity

Answer 18

Ability to accurate discern between those that do and those that do not have disease

Question 19

Internal Validity

Answer 19

Extent to which results accurately reflect what was being assessed

Question 20

External Validity

Answer 20

Extent to which results are applicable to other populations (Generalizability)

Question 21

Reliability

Answer 21

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

Question 22

What should LR+ be to demonstrate the test is most beneficial?

Answer 22

> 10

Question 23

What should LR- be to demonstrate the test is most beneficial?

Answer 23

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