From the Guidelines
A hematocrit level of 46.8% is considered elevated and requires immediate attention to reduce the risk of thrombosis, with a target hematocrit level of <45% being recommended to lower this risk. This elevation in hematocrit level can increase blood viscosity, potentially leading to a higher risk of blood clots, which can have significant implications for morbidity and mortality, particularly in patients with myeloproliferative neoplasms such as polycythemia vera (PV) 1.
The management of elevated hematocrit levels should involve a comprehensive evaluation, including repeat testing to confirm the result, checking other blood parameters like hemoglobin and red blood cell count, and investigating potential causes such as polycythemia vera, chronic lung disease, living at high altitude, smoking, or dehydration. According to the CYTO-PV trial, targeting a hematocrit level <45% can significantly reduce the composite primary endpoint of time until death from cardiovascular causes or major thrombotic events (HR in the high hematocrit group, 3.91; 95% CI, 1.45–10.53; P=0.007) 1.
Key considerations in the management of elevated hematocrit levels include:
- Confirming the result with repeat testing
- Checking other blood parameters like hemoglobin and red blood cell count
- Investigating potential causes such as polycythemia vera, chronic lung disease, living at high altitude, smoking, or dehydration
- Targeting a hematocrit level <45% to reduce the risk of thrombosis
- Considering lifestyle modifications like increasing hydration and avoiding tobacco
- Potential treatments like phlebotomy (blood removal) or medications such as hydroxyurea for more serious conditions like polycythemia vera. The use of low-dose aspirin may also be considered to prevent thrombotic complications, as shown in the ECLAP trial, which demonstrated a reduced risk of the combined endpoint of nonfatal myocardial infarction, nonfatal stroke, or death from cardiovascular causes (RR, 0.41; 95% CI, 0.15–1.15; P=0.09) 1.
From the Research
Implications of Elevated Hematocrit Level
An elevated hematocrit (Hct) level of 46.8, indicating erythrocytosis (high red blood cell count), can have several implications, including:
- Increased risk of thrombosis, as an elevated hematocrit is a risk factor for thrombosis 2, 3
- Possible diagnosis of polycythemia vera (PV), a myeloproliferative neoplasm characterized by an increased red blood cell mass and increased risk of thrombosis 4
- Association with other symptoms such as splenomegaly, aquagenic pruritus, and erythromelalgia, which are often present in PV 2, 4
- Need for further evaluation, including blood volume studies, to determine the cause of the elevated hematocrit and to rule out other conditions such as secondary polycythemia or relative polycythemia 2
Diagnostic Considerations
The diagnosis of PV or other conditions associated with erythrocytosis requires careful evaluation, including:
- Laboratory tests, such as complete blood count (CBC) and blood chemistry tests 4
- Physical examination, including evaluation for splenomegaly and other signs of PV 2, 4
- Molecular testing, such as JAK2 mutation analysis, to confirm the diagnosis of PV 4, 5
Treatment and Management
Treatment and management of PV and other conditions associated with erythrocytosis depend on the underlying cause and severity of the condition, and may include:
- Therapeutic phlebotomy to reduce the hematocrit level and prevent thrombosis 4, 5
- Low-dose aspirin to prevent thrombosis 4, 5
- Cytoreductive therapy, such as hydroxyurea or interferon, to reduce the risk of thrombosis and manage symptoms 4, 5
- Screening for acquired von Willebrand syndrome (AvWS) in patients with extreme thrombocytosis 5