laboratory tests

Question 1

What are the 4 major types of lab testing?

Answer 1

• diagnostic
• monitoring
• screening
• lifestyle/other (insurance company)

Question 2

Sensitivity=

Answer 2

TP/(TP+FN)

-the probability that a test will be positive when the disease is present.

Question 3

Specificity=

Answer 3

TN/(TN+FP)

-probability that a test result will be negative when disease is not present

Question 4

Positive Predictive Value (PPV)=

Answer 4

TP/(TP+FP)

-probability that a positive test result is associated with presence of disease

Question 5

NPV=

Answer 5

TN/(TN+FN)

-Probability that a negative test result is associated with absence of disease.

Question 6

Precision vs. accuracy

Answer 6

probability that repeating the test yields the same result

vs

how close yo are to the ‘real’ answer

Question 7

Diagnostic tests (high prevalence due to physician selection):

What specificity do we aim for?

Answer 7

> 95%

Question 8

Screening tests (low prevalence of condition):

what sensitivity do we aim for?

Answer 8

Want HIGH sensitivity to avoid FN, at cost of low specificity.

Question 9

Positive Likelihood Ratio (LR)=

Negative Likelihood Ratio (LR)=

Answer 9

sensitivity/ (1- specificity)

(1-sensitivity)/specificity