NR 511 Differential Diagnosis & Primary
Care Midterm Review ALL Questions &
Correct Answers & Clinical Rationales
Question 1:
A diagnostic test is evaluated using a sample of 200 men, 160 of whom have confirmed
prostate cancer. Among those with prostate cancer, the test yields positive results for all
160 individuals. What is the sensitivity of this test for detecting prostate cancer?
a. 40/200
b. 160/200
c. 160/160
d. 40/160
✔️ Correct Answer: C
Rationale:
Sensitivity is defined as the proportion of individuals with the disease who test positive,
calculated as true positives divided by the total number of individuals who have the
disease. In this scenario, all 160 men with prostate cancer tested positive, yielding a
sensitivity of 160/160 or 100%. Option A is incorrect because it represents the false-
negative rate. Option B is incorrect because it calculates the proportion of positive tests
,in the total sample. Option D is incorrect because it represents the false-negative rate in
the diseased population.
A diagnostic test is administered to a sample of 1,000 patients, of whom 500 have the
disease and 500 do not. Of the 500 patients without the disease, 30 test positive and 470
test negative. What is the specificity of this test?
a. 30/500
b. 470/500
c. 470/1000
d. 500/1000
✔️ Correct Answer: B
Rationale:
Specificity is the proportion of patients without the disease who correctly test negative,
calculated as true negatives divided by the total number of patients without the disease.
In this case, 470 true negatives divided by 500 disease-free patients equals 94%
specificity. Option A represents the false-positive rate. Option C incorrectly uses the total
sample as the denominator. Option D is the prevalence of disease in the sample.
The Positive Predictive Value (PPV) of a diagnostic test refers to which of the following?
a. The proportion of patients with a negative test who do not have the disease
b. The proportion of patients with a positive test who have the disease
c. The proportion of patients with the disease who test positive
d. The proportion of patients without the disease who test negative
✔️ Correct Answer: B
Rationale:
Positive Predictive Value (PPV) is defined as the likelihood that a patient with a positive
test result actually has the disease. It is calculated as true positives divided by all positive
test results. Option A describes the Negative Predictive Value (NPV). Option C describes
sensitivity. Option D describes specificity.
,Which of the following test characteristics depends on the prevalence of the disease in
the population?
a. Sensitivity
b. Specificity
c. Positive Predictive Value
d. Reliability
✔️ Correct Answer: C
Rationale:
Predictive values, including Positive Predictive Value and Negative Predictive Value, are
influenced by disease prevalence. As prevalence increases, PPV increases and NPV
decreases. Sensitivity and specificity are intrinsic properties of the test and do not vary
with prevalence. Reliability refers to the consistency of measurement.
A low pretest probability of disease in a population will most likely result in which of the
following?
a. Low positive predictive value and more false-positive results
b. High positive predictive value and more false-negative results
c. Low sensitivity and high specificity
d. High negative predictive value and fewer false positives
✔️ Correct Answer: A
Rationale:
When disease prevalence is low, the positive predictive value decreases because there are
proportionally more false-positive results. Negative predictive value increases with lower
prevalence. Sensitivity and specificity remain unchanged as they are properties of the test
itself.
If a clinician strongly suspects that a patient has a specific condition but the diagnostic
test returns negative, the negative result is most likely explained by:
a. High sensitivity of the test
b. Low negative predictive value
, c. High specificity of the test
d. Low prevalence of the disease
✔️ Correct Answer: B
Rationale:
When clinical suspicion (pretest probability) is high, the negative predictive value
decreases, meaning a negative result is more likely to be a false negative. The clinician's
suspicion reflects high prevalence in the individual context. Options A and C describe test
properties that would make a negative result more reliable, which contradicts the
scenario. Option D would actually increase NPV.
A patient presents with a chief complaint of fever. Which diagnostic test would provide
the most relevant data for evaluating this symptom?
a. Complete Blood Count with differential
b. Basic Metabolic Panel
c. Liver Function Tests
d. Thyroid Stimulating Hormone
✔️ Correct Answer: A
Rationale:
A Complete Blood Count with differential is the most appropriate initial test for
evaluating fever, as it can reveal leukocytosis with a left shift, which suggests bacterial
infection. Option B assesses electrolytes and renal function. Option C evaluates liver
function. Option D assesses thyroid function, which is not primarily associated with fever.
A patient presents with a chief complaint of unexplained bruising. Which diagnostic test
should the clinician order?
a. Complete Blood Count with platelet count
b. Prothrombin Time
c. Partial Thromboplastin Time
d. Comprehensive Metabolic Panel
✔️ Correct Answer: A
Rationale:
Care Midterm Review ALL Questions &
Correct Answers & Clinical Rationales
Question 1:
A diagnostic test is evaluated using a sample of 200 men, 160 of whom have confirmed
prostate cancer. Among those with prostate cancer, the test yields positive results for all
160 individuals. What is the sensitivity of this test for detecting prostate cancer?
a. 40/200
b. 160/200
c. 160/160
d. 40/160
✔️ Correct Answer: C
Rationale:
Sensitivity is defined as the proportion of individuals with the disease who test positive,
calculated as true positives divided by the total number of individuals who have the
disease. In this scenario, all 160 men with prostate cancer tested positive, yielding a
sensitivity of 160/160 or 100%. Option A is incorrect because it represents the false-
negative rate. Option B is incorrect because it calculates the proportion of positive tests
,in the total sample. Option D is incorrect because it represents the false-negative rate in
the diseased population.
A diagnostic test is administered to a sample of 1,000 patients, of whom 500 have the
disease and 500 do not. Of the 500 patients without the disease, 30 test positive and 470
test negative. What is the specificity of this test?
a. 30/500
b. 470/500
c. 470/1000
d. 500/1000
✔️ Correct Answer: B
Rationale:
Specificity is the proportion of patients without the disease who correctly test negative,
calculated as true negatives divided by the total number of patients without the disease.
In this case, 470 true negatives divided by 500 disease-free patients equals 94%
specificity. Option A represents the false-positive rate. Option C incorrectly uses the total
sample as the denominator. Option D is the prevalence of disease in the sample.
The Positive Predictive Value (PPV) of a diagnostic test refers to which of the following?
a. The proportion of patients with a negative test who do not have the disease
b. The proportion of patients with a positive test who have the disease
c. The proportion of patients with the disease who test positive
d. The proportion of patients without the disease who test negative
✔️ Correct Answer: B
Rationale:
Positive Predictive Value (PPV) is defined as the likelihood that a patient with a positive
test result actually has the disease. It is calculated as true positives divided by all positive
test results. Option A describes the Negative Predictive Value (NPV). Option C describes
sensitivity. Option D describes specificity.
,Which of the following test characteristics depends on the prevalence of the disease in
the population?
a. Sensitivity
b. Specificity
c. Positive Predictive Value
d. Reliability
✔️ Correct Answer: C
Rationale:
Predictive values, including Positive Predictive Value and Negative Predictive Value, are
influenced by disease prevalence. As prevalence increases, PPV increases and NPV
decreases. Sensitivity and specificity are intrinsic properties of the test and do not vary
with prevalence. Reliability refers to the consistency of measurement.
A low pretest probability of disease in a population will most likely result in which of the
following?
a. Low positive predictive value and more false-positive results
b. High positive predictive value and more false-negative results
c. Low sensitivity and high specificity
d. High negative predictive value and fewer false positives
✔️ Correct Answer: A
Rationale:
When disease prevalence is low, the positive predictive value decreases because there are
proportionally more false-positive results. Negative predictive value increases with lower
prevalence. Sensitivity and specificity remain unchanged as they are properties of the test
itself.
If a clinician strongly suspects that a patient has a specific condition but the diagnostic
test returns negative, the negative result is most likely explained by:
a. High sensitivity of the test
b. Low negative predictive value
, c. High specificity of the test
d. Low prevalence of the disease
✔️ Correct Answer: B
Rationale:
When clinical suspicion (pretest probability) is high, the negative predictive value
decreases, meaning a negative result is more likely to be a false negative. The clinician's
suspicion reflects high prevalence in the individual context. Options A and C describe test
properties that would make a negative result more reliable, which contradicts the
scenario. Option D would actually increase NPV.
A patient presents with a chief complaint of fever. Which diagnostic test would provide
the most relevant data for evaluating this symptom?
a. Complete Blood Count with differential
b. Basic Metabolic Panel
c. Liver Function Tests
d. Thyroid Stimulating Hormone
✔️ Correct Answer: A
Rationale:
A Complete Blood Count with differential is the most appropriate initial test for
evaluating fever, as it can reveal leukocytosis with a left shift, which suggests bacterial
infection. Option B assesses electrolytes and renal function. Option C evaluates liver
function. Option D assesses thyroid function, which is not primarily associated with fever.
A patient presents with a chief complaint of unexplained bruising. Which diagnostic test
should the clinician order?
a. Complete Blood Count with platelet count
b. Prothrombin Time
c. Partial Thromboplastin Time
d. Comprehensive Metabolic Panel
✔️ Correct Answer: A
Rationale:
