BBH 440 FINAL EXAM QUESTIONS &
DETAILED COMPLETE SOLUTIONS
100%
Screening - correct answer ✔✔-accomplishes early detention of a disease in asymptomatic
people
-usually NOT diagnostic tests
-person who screens (+) are given further diagnostic tests like biopsies to confirm it
-usually inexpensive, simple, valid and reliable for people who MIGHT have the disease
-form of secondary prevention
-improves outcomes
Common Screening Tests - correct answer ✔✔Physical Health Related
-Glaucoma (intra-ocular pressure)
-Diabetes (blood sugar, HbA1c)
-Blood Pressure (self-exam)
-Breast Cancer (breast self-exam (BSE); mammogram)
-Testicular Cancer (self exam)
-Prostate Cancer (Digital Rectal Exam (DRE), Prostate Specific Antigen (PSA))
Mental Health, Other
-Alcoholism
-Depression
,Natural History of a Disease - correct answer ✔✔Biological onset-->Disease detection by
screening-->Symptoms develop-->Death
-Detectable Pre-Clinical Phase (DPCP): between disease detection and symptoms
Requirements for a screening program - correct answer ✔✔1. Suitable disease
2. Suitable test: reliable and valide
3. Suitable program: program surrounding the effort to help the person get treatment,
counseling, etc.
4. Good use of resources: cost effective and yields significant results
Possible outcomes of a screening test - correct answer ✔✔-True positive
-True negative
-False negative- test negative but DO have it
-False positive- test positive but DO NOT have it
Sensitivity - correct answer ✔✔-tells how well a test picks up disease
-defined by fraction of diseases who test positive: TP/(TP+FN)
-also called true positive rate and answers "if a person has a disease, how often will the test be
positive?"
-its complement is the false negative rate, defined as the fraction of the diseased who test
negative (sensitivity and false negative rate add up to one)
Specificity - correct answer ✔✔-tells us how well a test identifies non-disease
-defined as the fraction of the non-diseased who test negative: TN/(FP+TN)
-it is also called the true negative rate and answers the question "if a person does not have the
disease, how often will the test be negative?"
, Is it more important that a test be sensitive or specific? - correct answer ✔✔-depends on the
purpose
-a cheap mass screening test should be sensitive (few cases missed) and generally sensitivity is
extremely important
-in certain situations it may be very important to have a test with high specificity
-sensitivity and specificity are 2 distinct properties. Some situations require tradeoffs to be
made between the two
Predictive Value - correct answer ✔✔-POSITIVE predictive value is the proportion of all people
with positive tests who have the disease: TP/(TP+FP)
-NEGATIVE predictive value is the proportion of all people with negative tests who do not have
the disease: TN/(FN+TN)
-positive is usually the most used.
-positive predictive value and sensitivity are generally extremely important parameters in
understanding the usefulness of a screening test under real-life conditions
Sensitivity, specificity and predictive values - correct answer ✔✔-specificity, sensitivity, false
positive and false negative rates are denominatored to diseased or non-diseased individuals
-predictive values are denominatored to test status, positive or negative
-predictive values are heavily affected by the prevalence of the disease in the population
positive and negative predictive values - correct answer ✔✔-PPV and NPV are useful in
determining probability after (+) or (-) tests
-however they are sensitive to prevalence of disease
-prevalence of disease in general population may not be the same as that of patients you see in
clinic/ER
-for these reasons, some clinicians prefer to use "likelihood ratios"
DETAILED COMPLETE SOLUTIONS
100%
Screening - correct answer ✔✔-accomplishes early detention of a disease in asymptomatic
people
-usually NOT diagnostic tests
-person who screens (+) are given further diagnostic tests like biopsies to confirm it
-usually inexpensive, simple, valid and reliable for people who MIGHT have the disease
-form of secondary prevention
-improves outcomes
Common Screening Tests - correct answer ✔✔Physical Health Related
-Glaucoma (intra-ocular pressure)
-Diabetes (blood sugar, HbA1c)
-Blood Pressure (self-exam)
-Breast Cancer (breast self-exam (BSE); mammogram)
-Testicular Cancer (self exam)
-Prostate Cancer (Digital Rectal Exam (DRE), Prostate Specific Antigen (PSA))
Mental Health, Other
-Alcoholism
-Depression
,Natural History of a Disease - correct answer ✔✔Biological onset-->Disease detection by
screening-->Symptoms develop-->Death
-Detectable Pre-Clinical Phase (DPCP): between disease detection and symptoms
Requirements for a screening program - correct answer ✔✔1. Suitable disease
2. Suitable test: reliable and valide
3. Suitable program: program surrounding the effort to help the person get treatment,
counseling, etc.
4. Good use of resources: cost effective and yields significant results
Possible outcomes of a screening test - correct answer ✔✔-True positive
-True negative
-False negative- test negative but DO have it
-False positive- test positive but DO NOT have it
Sensitivity - correct answer ✔✔-tells how well a test picks up disease
-defined by fraction of diseases who test positive: TP/(TP+FN)
-also called true positive rate and answers "if a person has a disease, how often will the test be
positive?"
-its complement is the false negative rate, defined as the fraction of the diseased who test
negative (sensitivity and false negative rate add up to one)
Specificity - correct answer ✔✔-tells us how well a test identifies non-disease
-defined as the fraction of the non-diseased who test negative: TN/(FP+TN)
-it is also called the true negative rate and answers the question "if a person does not have the
disease, how often will the test be negative?"
, Is it more important that a test be sensitive or specific? - correct answer ✔✔-depends on the
purpose
-a cheap mass screening test should be sensitive (few cases missed) and generally sensitivity is
extremely important
-in certain situations it may be very important to have a test with high specificity
-sensitivity and specificity are 2 distinct properties. Some situations require tradeoffs to be
made between the two
Predictive Value - correct answer ✔✔-POSITIVE predictive value is the proportion of all people
with positive tests who have the disease: TP/(TP+FP)
-NEGATIVE predictive value is the proportion of all people with negative tests who do not have
the disease: TN/(FN+TN)
-positive is usually the most used.
-positive predictive value and sensitivity are generally extremely important parameters in
understanding the usefulness of a screening test under real-life conditions
Sensitivity, specificity and predictive values - correct answer ✔✔-specificity, sensitivity, false
positive and false negative rates are denominatored to diseased or non-diseased individuals
-predictive values are denominatored to test status, positive or negative
-predictive values are heavily affected by the prevalence of the disease in the population
positive and negative predictive values - correct answer ✔✔-PPV and NPV are useful in
determining probability after (+) or (-) tests
-however they are sensitive to prevalence of disease
-prevalence of disease in general population may not be the same as that of patients you see in
clinic/ER
-for these reasons, some clinicians prefer to use "likelihood ratios"
