From the Guidelines
The initial workup for suspected polycythemia should begin with a complete blood count (CBC) with differential to confirm the elevated red blood cell count, hemoglobin, and hematocrit levels, followed by measurement of erythropoietin (EPO) levels to help distinguish between primary and secondary causes, as suggested by 1.
Initial Steps
The diagnostic possibility of polycythemia vera (PV) may be entertained if the hemoglobin/hematocrit level is higher than the 95th percentile of the normal distribution adjusted for sex and race, or if there is a documented increase in the hemoglobin/hematocrit level above the baseline for an individual patient, regardless of where the specific hematocrit level lies within the reference range, as noted in 1.
- A CBC with differential is essential to confirm the diagnosis and rule out other causes of elevated red blood cell count.
- Measurement of EPO levels can help distinguish between primary and secondary causes of polycythemia, with low EPO levels being highly suggestive but not diagnostic of PV, as stated in 1.
Additional Tests
Additional first-line tests may include:
- Comprehensive metabolic panel to evaluate for any underlying metabolic disorders.
- Arterial blood gas analysis to assess oxygen saturation and rule out hypoxia as a cause of secondary polycythemia.
- JAK2 V617F mutation testing, which is positive in approximately 95% of polycythemia vera cases, as mentioned in the example answer.
- Abdominal ultrasound to evaluate spleen size, as splenomegaly is common in primary polycythemia.
Further Evaluation
If JAK2 is negative but clinical suspicion remains high, bone marrow biopsy and aspiration should be performed to evaluate cellularity and morphology, as suggested by 1.
- Serum ferritin should be checked to rule out iron deficiency as a cause of relative polycythemia. These tests help differentiate between primary polycythemia vera, secondary polycythemia due to hypoxia or inappropriate EPO production, and relative polycythemia (Gaisböck syndrome) where plasma volume is decreased rather than true red cell mass elevation, as discussed in 1.
From the Research
Initial Workup for Suspected Polycythemia
The initial workup for suspected polycythemia involves several steps to determine the underlying cause of the condition.
- Erythrocytosis, characterized by an elevated hemoglobin or hematocrit level, is a key diagnostic criterion for polycythemia vera (PV) 2, 3.
- A complete blood cell count (CBC) is essential to evaluate the patient's red blood cell count, white blood cell count, and platelet count 4.
- Bone marrow biopsy and histomorphology are crucial in distinguishing PV from other myeloproliferative neoplasms (MPNs) and in establishing a baseline for future comparisons 5.
- Molecular testing for the JAK2 gene variant is also important, as it is present in approximately 95% of patients with PV 2 and helps differentiate PV from secondary causes of erythrocytosis.
Diagnostic Criteria
The World Health Organization's major diagnostic criteria for PV include:
- Elevated hemoglobin or hematocrit level
- Abnormal bone marrow biopsy results
- Presence of the JAK2 gene variant
- Subnormal erythropoietin level (minor criterion) 3
Laboratory Tests
Laboratory tests that may be ordered as part of the initial workup include:
- Hemoglobin and hematocrit levels
- Red blood cell count and indices
- White blood cell count and differential
- Platelet count
- Erythropoietin level
- JAK2 mutation testing
- Bone marrow biopsy and histomorphology 2, 5, 4
Clinical Evaluation
A thorough clinical evaluation is also essential in the initial workup for suspected polycythemia.
- Patients should be evaluated for signs and symptoms of PV, such as pruritus, erythromelalgia, transient visual changes, and splenomegaly 2.
- A detailed medical history should be obtained to identify potential causes of secondary erythrocytosis, such as tobacco smoking or sleep apnea 2, 6.
- Patients should also be assessed for risk factors for thrombosis, such as age and history of thrombotic events 2, 3.