GORDIS EPIDEMIOLOGY CELENTANO KEY
CONCEPTS AND PRACTICE QUESTIONS
◉ unimodal curve
Answer: a graph with one peak, for example, blood pressure
readings
◉ what is the validity of a test? What are its two components?
Answer: it's ability to distinguish between who has a disease and
who does not. Sensitivity and specificity
◉ Sensitivity (true positives)
Answer: the proportion of diseased people who were correctly
identified as "positive" by the test. TOTAL WITH DISEASE IN
DENOMINATOR
◉ Specificity (true negatives)
Answer: the proportion of NON-diseased people who were correctly
identified as "negative" by the test. TOTAL WITHOUT DISEASE IN
DENOMINATOR
◉ Sequential (two-stage) Screening
,Answer: a less expensive, less invasive test is performed first, and
those who screen positive are recalled for further testing with a
more expensive, more invasive test
◉ How to calculate net sensitivity and specificity in a two-stage
screening program
Answer: Take the numbers from a, b, and a+b from the first test and
make that the bottom total in the second test. Run the test. Then
calculate sensitivity and specificity as you would
◉ Sequential testing results in a gain of ___________ and a loss of
_______?
Answer: Net specificity net sensitivity
◉ Simultaneous Screening
Answer: Do both tests at once
◉ How to be considered a true positive and true negative in
simultaneous screening
Answer: Positive: only need one positive result
Negative: BOTH tests must be negative
◉ How to calculate net sensitivity in a simultaneous test
Answer: 1. Find the number of true positives in Test A
, 2. Run Test B's sensitivity on that number. This is the number of true
positives found by both tests A and B.
3. To find the number of true positives found ONLY in Test A,
subtract it from the the number found in step 2.
4. Do the opposite for test B.
5. Add test A only, Test B only, and both tests
◉ Using a simultaneous test results in a net gain of ______ and net
loss in _______
Answer: Gain in sensitivity and loss in specificity
◉ What is in the denominator when calculating sensitivity?
Answer: People who have the disease
◉ What is in the denominator when calculating specificity?
Answer: People who do NOT have the disease
◉ What is the positive predictive value?
Answer: Focuses on the screening test, not the disease. What is the
chance that someone has the disease IF THEY TESTED POSITIVE
◉ What is negative predictive value?
CONCEPTS AND PRACTICE QUESTIONS
◉ unimodal curve
Answer: a graph with one peak, for example, blood pressure
readings
◉ what is the validity of a test? What are its two components?
Answer: it's ability to distinguish between who has a disease and
who does not. Sensitivity and specificity
◉ Sensitivity (true positives)
Answer: the proportion of diseased people who were correctly
identified as "positive" by the test. TOTAL WITH DISEASE IN
DENOMINATOR
◉ Specificity (true negatives)
Answer: the proportion of NON-diseased people who were correctly
identified as "negative" by the test. TOTAL WITHOUT DISEASE IN
DENOMINATOR
◉ Sequential (two-stage) Screening
,Answer: a less expensive, less invasive test is performed first, and
those who screen positive are recalled for further testing with a
more expensive, more invasive test
◉ How to calculate net sensitivity and specificity in a two-stage
screening program
Answer: Take the numbers from a, b, and a+b from the first test and
make that the bottom total in the second test. Run the test. Then
calculate sensitivity and specificity as you would
◉ Sequential testing results in a gain of ___________ and a loss of
_______?
Answer: Net specificity net sensitivity
◉ Simultaneous Screening
Answer: Do both tests at once
◉ How to be considered a true positive and true negative in
simultaneous screening
Answer: Positive: only need one positive result
Negative: BOTH tests must be negative
◉ How to calculate net sensitivity in a simultaneous test
Answer: 1. Find the number of true positives in Test A
, 2. Run Test B's sensitivity on that number. This is the number of true
positives found by both tests A and B.
3. To find the number of true positives found ONLY in Test A,
subtract it from the the number found in step 2.
4. Do the opposite for test B.
5. Add test A only, Test B only, and both tests
◉ Using a simultaneous test results in a net gain of ______ and net
loss in _______
Answer: Gain in sensitivity and loss in specificity
◉ What is in the denominator when calculating sensitivity?
Answer: People who have the disease
◉ What is in the denominator when calculating specificity?
Answer: People who do NOT have the disease
◉ What is the positive predictive value?
Answer: Focuses on the screening test, not the disease. What is the
chance that someone has the disease IF THEY TESTED POSITIVE
◉ What is negative predictive value?
