NR 511 Differential Diagnosis & Primary
Care Midterm Review ALL Questions &
Correct Answers & Clinical Rationales
Question 1:
What is the sensitivity of the Prostate Specific Antigen (PSA) for detecting prostate
cancer?
• men with prostate cancer
• men with positive PSA: 160
• men with negative PSA: 40
• total: 200
Answer:
The correct answer is 160/200. Sensitivity is the proportion of patients with the
disease that have a positive result; it is the number of true positives divided by the
total number of patients who have the disease.
Question 2:
,A diagnostic test is used in a sample of 1000 patients. 500 of these patients have
the disease, while 500 do not. Of those 500 patients without the disease, 30 test
positive, and 470 test negative. What is the specificity of the test?
Answer:
The correct answer is 470/500.
Specificity is the proportion of patients who test negative out of the total number
of patients who do not have the disease; it is the number of true negatives overall
negatives. In this example, 500/1000 patients have the disease. Of those 500
patients without the disease, 30 test positive, and 470 test negative.
Question 3:
The Positive Predictive Value (PPV) of a test refers to which of the following?
Answer:
The proportion of patients with a positive test who have the disease.
Question 4:
Which of the following depends on the prevalence of the disease?
Answer:
Positive predictive value.
Predictive values depend on the prevalence of disease in the population whereas
sensitivity and specificity are intrinsic properties of the test. Reliability refers to
the consistency or stability of a measure.
Question 5:
A low pretest probability of disease may lead to which of the following?
Answer:
Low positive predictive value and more false-positive results.
,Positive predictive value increases with prevalence; therefore, a low prevalence
value yields a low positive predictive value and implies a high false-positive rate.
Negative predictive value decreases with prevalence, and sensitivity and
specificity do not vary with prevalence.
Question 6:
If you strongly suspect that a patient is positive for a specific condition but tests
negative, the negative result may be:
Answer:
False-negative test results due to a low negative predictive value.
At the individual level, your clinical suspicion is equivalent to pre-test probability
and high prevalence at the population level. Negative predictive value is inversely
correlated with prevalence; therefore, your clinical suspicion translates to a low
negative predictive value, suggesting a false-negative test result.
Question 7:
Which test(s) provide data relevant to the chief complaint: Fever?
Answer:
CBC.
Check CBC with differential for neutrophil shift in suspected infection.
Question 8:
Which test(s) provide data relevant to the chief complaint: Unexplained bruising?
Answer:
CBC.
Check platelet count.
, Question 9:
Which test(s) provide data relevant to the chief complaint: Fatigue?
Answer:
Both CBC and CMP.
Check RBC, Hgb and Hct for anemia; CMP for potential liver or kidney
abnormalities.
Question 10:
Which test(s) provide data relevant to the chief complaint: Cardiac dysrhythmias?
Answer:
CMP.
Monitor electrolytes for abnormalities.
Question 11:
Which test(s) provide data relevant to the chief complaint: Unexplained weight
loss?
Answer:
Both CBC and CMP.
Check WBC for inflammation or possible cancer; CMP for glucose, liver or kidney
abnormalities.
Question 12:
Which test(s) provide data relevant to the chief complaint: Edema?
Answer:
CMP.
Check for kidney function.
Care Midterm Review ALL Questions &
Correct Answers & Clinical Rationales
Question 1:
What is the sensitivity of the Prostate Specific Antigen (PSA) for detecting prostate
cancer?
• men with prostate cancer
• men with positive PSA: 160
• men with negative PSA: 40
• total: 200
Answer:
The correct answer is 160/200. Sensitivity is the proportion of patients with the
disease that have a positive result; it is the number of true positives divided by the
total number of patients who have the disease.
Question 2:
,A diagnostic test is used in a sample of 1000 patients. 500 of these patients have
the disease, while 500 do not. Of those 500 patients without the disease, 30 test
positive, and 470 test negative. What is the specificity of the test?
Answer:
The correct answer is 470/500.
Specificity is the proportion of patients who test negative out of the total number
of patients who do not have the disease; it is the number of true negatives overall
negatives. In this example, 500/1000 patients have the disease. Of those 500
patients without the disease, 30 test positive, and 470 test negative.
Question 3:
The Positive Predictive Value (PPV) of a test refers to which of the following?
Answer:
The proportion of patients with a positive test who have the disease.
Question 4:
Which of the following depends on the prevalence of the disease?
Answer:
Positive predictive value.
Predictive values depend on the prevalence of disease in the population whereas
sensitivity and specificity are intrinsic properties of the test. Reliability refers to
the consistency or stability of a measure.
Question 5:
A low pretest probability of disease may lead to which of the following?
Answer:
Low positive predictive value and more false-positive results.
,Positive predictive value increases with prevalence; therefore, a low prevalence
value yields a low positive predictive value and implies a high false-positive rate.
Negative predictive value decreases with prevalence, and sensitivity and
specificity do not vary with prevalence.
Question 6:
If you strongly suspect that a patient is positive for a specific condition but tests
negative, the negative result may be:
Answer:
False-negative test results due to a low negative predictive value.
At the individual level, your clinical suspicion is equivalent to pre-test probability
and high prevalence at the population level. Negative predictive value is inversely
correlated with prevalence; therefore, your clinical suspicion translates to a low
negative predictive value, suggesting a false-negative test result.
Question 7:
Which test(s) provide data relevant to the chief complaint: Fever?
Answer:
CBC.
Check CBC with differential for neutrophil shift in suspected infection.
Question 8:
Which test(s) provide data relevant to the chief complaint: Unexplained bruising?
Answer:
CBC.
Check platelet count.
, Question 9:
Which test(s) provide data relevant to the chief complaint: Fatigue?
Answer:
Both CBC and CMP.
Check RBC, Hgb and Hct for anemia; CMP for potential liver or kidney
abnormalities.
Question 10:
Which test(s) provide data relevant to the chief complaint: Cardiac dysrhythmias?
Answer:
CMP.
Monitor electrolytes for abnormalities.
Question 11:
Which test(s) provide data relevant to the chief complaint: Unexplained weight
loss?
Answer:
Both CBC and CMP.
Check WBC for inflammation or possible cancer; CMP for glucose, liver or kidney
abnormalities.
Question 12:
Which test(s) provide data relevant to the chief complaint: Edema?
Answer:
CMP.
Check for kidney function.
