PV

Question 1

What is the first step in evaluating a patient with elevated hemoglobin (hgb) or hematocrit (hct)?
A. Measure serum EPO levels
B. Confirm JAK2 mutation
C. Measure RBC mass
D. Perform CT imaging

Answer 1

Correct Answer: C
Rationale: The flowchart begins with measuring the RBC mass to differentiate between true and relative erythrocytosis. If RBC mass is normal, the diagnosis is relative erythrocytosis.

Question 2

If RBC mass is elevated and serum erythropoietin (EPO) levels are low, what is the likely diagnosis?
A. Smoker’s polycythemia
B. Polycythemia vera
C. COPD
D. High-altitude erythrocytosis

Answer 2

Correct Answer: B
Rationale: Low serum EPO levels with elevated RBC mass indicate polycythemia vera, a myeloproliferative disorder often confirmed with JAK2 mutation testing.

Question 3

In a patient with elevated hemoglobin and high serum EPO levels, what should be assessed next?
A. JAK2 mutation
B. Arterial oxygen saturation
C. Hemoglobin oxygen affinity
D. Carboxyhemoglobin levels

Answer 3

Correct Answer: B
Rationale: High serum EPO levels indicate secondary erythrocytosis. Arterial oxygen saturation is measured next to assess for hypoxic causes such as heart or lung diseases, high altitude, or shunting.

Question 4

What is the next step if arterial oxygen saturation is normal in a patient with high EPO levels?
A. Measure hemoglobin oxygen affinity
B. Measure carboxyhemoglobin levels
C. Perform imaging studies to locate a tumor
D. Confirm JAK2 mutation

Answer 4

Correct Answer: B
Rationale: If oxygen saturation is normal, assessing carboxyhemoglobin levels helps rule out smoker’s polycythemia as a cause of erythrocytosis.