Epidemiology

Question 1

What are the parts of PICO?

Answer 1

• patients (population)
• intervention (experimental group)
• comparison (control group)
• outcome

Question 2

What drags down sensitivity?

Answer 2

False negatives

Sensitivity + FNR = 100%

Question 3

Formula and definition of sensitivity

Answer 3

Sensitivity = a / (a+c)

• true positive rate
• what percent of ppl w/ the disease get a positive test result

Question 4

Formula and definition of specificity

Answer 4

Specificity = d / (b+d)

• true negative rate
• what percent of ppl w/o the disease get a negative result

Question 5

What is the real value of interest of a test result

Answer 5

Positive predictive value (which = posttest probability)

-value of ppl w/ a positive result who truly have teh disease

Question 6

Formula and definition of PPV

Answer 6

+PV = a / (a+b)

-proportion of ppl w/ a positive test result who actually have the disease

Question 7

Formula and definition of NPV

Answer 7

• PV = d / (c+d)

- proportion of ppl w/ a negative test result who truly don’t have the disease

Question 8

What result from what kind of test would rule a diagnosis in ?

Answer 8

SpPIN

-positive result on a specific test (low false positives) rules in a diagnosis

Question 9

What results from what kind of test would rule out a diagnosis?

Answer 9

SnNOUT

-negative result on a sensitivity test (low false negative) rules out a diagnosis

Question 10

Describe what a likelihood ratio is

Answer 10

LR is one test result for two populations

ex] LR of 11 means that the test results are 11 times more likely in a patient with the disease than in a patient without the disease

Question 11

Describe how to get from pretest probability to posttest probability

Answer 11

Pretest odds = (pretest probability) / (1- pretest probability)

Pretest odds x LR = post test odds

Post test probability = (posttest odds) / (posttest odds + 1)