GORDIS EPIDEMIOLOGY 6TH EDITION TEST
BANK COMPLETE QUESTIONS AND VERIFIED
ANSWERS
What is a bimodal curve - a graph with two peaks that separates, for example, those
who have tuberculosis vs. those who do not from a screening test
unimodal curve - a graph with one peak, for example, blood pressure readings
what is the validity of a test? What are its two components? - it's ability to distinguish
between who has a disease and who does not. Sensitivity and specificity
Sensitivity (true positives) - the proportion of diseased people who were correctly
identified as "positive" by the test. TOTAL WITH DISEASE IN DENOMINATOR
Specificity (true negatives) - the proportion of NON-diseased people who were correctly
identified as "negative" by the test. TOTAL WITHOUT DISEASE IN DENOMINATOR
Sequential (two-stage) Screening - 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 - 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 _______? - Net
specificity net sensitivity
Simultaneous Screening - Do both tests at once
How to be considered a true positive and true negative in simultaneous screening -
Positive: only need one positive result
Negative: BOTH tests must be negative
How to calculate net sensitivity in a simultaneous test - 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 _______ -
Gain in sensitivity and loss in specificity
What is in the denominator when calculating sensitivity? - People who have the disease
What is in the denominator when calculating specificity? - People who do NOT have the
disease
What is the positive predictive value? - 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? - What is the chance that someone does not have
the disease IF THEY SCREENED NEGATIVE
Positive predictive value equation - True positives/all who tested positive
Negative predictive value equation - true negatives/all who tested negative
What two factors is the positive predictive value affected by? - 1. prevalence of disease
2. specificity when the disease is rare
Relationship between positive predictive value and prevalence - direct - a high
prevalence raises the positive predictive value. Therefore, best for high-risk populations
Relationship between positive predictive value and specificity of the test - direct - an
increase in specificity raises the the positive predictive value
BANK COMPLETE QUESTIONS AND VERIFIED
ANSWERS
What is a bimodal curve - a graph with two peaks that separates, for example, those
who have tuberculosis vs. those who do not from a screening test
unimodal curve - a graph with one peak, for example, blood pressure readings
what is the validity of a test? What are its two components? - it's ability to distinguish
between who has a disease and who does not. Sensitivity and specificity
Sensitivity (true positives) - the proportion of diseased people who were correctly
identified as "positive" by the test. TOTAL WITH DISEASE IN DENOMINATOR
Specificity (true negatives) - the proportion of NON-diseased people who were correctly
identified as "negative" by the test. TOTAL WITHOUT DISEASE IN DENOMINATOR
Sequential (two-stage) Screening - 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 - 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 _______? - Net
specificity net sensitivity
Simultaneous Screening - Do both tests at once
How to be considered a true positive and true negative in simultaneous screening -
Positive: only need one positive result
Negative: BOTH tests must be negative
How to calculate net sensitivity in a simultaneous test - 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 _______ -
Gain in sensitivity and loss in specificity
What is in the denominator when calculating sensitivity? - People who have the disease
What is in the denominator when calculating specificity? - People who do NOT have the
disease
What is the positive predictive value? - 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? - What is the chance that someone does not have
the disease IF THEY SCREENED NEGATIVE
Positive predictive value equation - True positives/all who tested positive
Negative predictive value equation - true negatives/all who tested negative
What two factors is the positive predictive value affected by? - 1. prevalence of disease
2. specificity when the disease is rare
Relationship between positive predictive value and prevalence - direct - a high
prevalence raises the positive predictive value. Therefore, best for high-risk populations
Relationship between positive predictive value and specificity of the test - direct - an
increase in specificity raises the the positive predictive value
