From the Guidelines
Polycythemia is typically identified on a CBC by elevated red blood cell parameters, including increased red blood cell count, hemoglobin, and hematocrit, and diagnosis requires the presence of specific criteria, including laboratory evidence of increased hemoglobin, hematocrit, or red cell mass and the presence of a JAK2 mutation, as proposed by the 2007 WHO criteria revision 1.
Key Diagnostic Criteria
- Elevated red blood cell count (typically >6.0 million/μL for men or >5.5 million/μL for women)
- Elevated hemoglobin (>18.5 g/dL for men or >16.5 g/dL for women)
- Increased hematocrit (>49% for men or >48% for women)
- Presence of JAK2 mutation
- Absence of secondary causes of erythrocytosis
Further Testing and Diagnosis
If polycythemia is suspected based on CBC results, further testing is recommended, including:
- JAK2 mutation analysis
- Erythropoietin levels
- Possibly bone marrow biopsy to distinguish between primary polycythemia (polycythemia vera) and secondary causes like hypoxia, smoking, or certain kidney or liver diseases
Treatment and Management
Treatment depends on the underlying cause but may include:
- Phlebotomy to reduce blood thickness
- Low-dose aspirin to prevent clotting
- In some cases, medications like hydroxyurea to reduce blood cell production, with consideration of resistance or intolerance to hydroxyurea as defined by the European LeukemiaNet 1 These elevated blood parameters are concerning because they increase blood viscosity, raising the risk of blood clots, strokes, and heart attacks, and management should prioritize minimizing these risks while addressing the underlying cause of polycythemia.
From the Research
Polycythemia Vera and CBC Results
Polycythemia vera (PV) is a myeloproliferative neoplasm characterized by an increased red blood cell mass and increased risk of thrombosis 2. The diagnosis of PV is based on the presence of erythrocytosis, which is defined as a hemoglobin level greater than 16.5 mg/dL in men or greater than 16.0 mg/dL in women 2.
CBC Results in PV
- Erythrocytosis (hemoglobin >16.5 mg/dL in men or >16.0 mg/dL in women) is a required diagnostic criterion for PV 2
- Thrombocytosis (53%) and leukocytosis (49%) are common in PV patients 2
- Patients with PV may have pruritus (33%), erythromelalgia (5.3%), transient visual changes (14%), and splenomegaly (36%) with abdominal discomfort 2
Treatment and Management
- All patients with PV should receive therapeutic phlebotomy (goal hematocrit, <45%) and low-dose aspirin (if no contraindications) 2
- Patients who are at higher risk of thrombosis, such as those aged 60 years or older or with a prior thrombosis, may benefit from cytoreductive therapy with hydroxyurea or interferon to lower thrombosis risk and decrease symptoms 2, 3
- Ruxolitinib is a Janus kinase inhibitor that can alleviate pruritus and decrease splenomegaly in patients who are intolerant of or resistant to hydroxyurea 2