Management of Elevated Hemoglobin and Hematocrit
Your patient's values (RBC 5.98, Hgb 17.8 g/dL, Hct 53.9%) represent erythrocytosis that requires systematic evaluation to distinguish primary polycythemia vera from secondary causes, but immediate therapeutic phlebotomy is NOT indicated at these levels. 1
Immediate Diagnostic Workup
Order the following tests immediately:
- Complete blood count with red cell indices (MCV, MCH, MCHC) to assess for iron deficiency, which commonly coexists with erythrocytosis 1
- Reticulocyte count to evaluate bone marrow response 1
- Peripheral blood smear to identify morphologic abnormalities 1
- Serum ferritin and transferrin saturation to detect iron deficiency, as MCV is unreliable for screening in erythrocytosis 1
- JAK2 mutation testing (both exon 14 and exon 12) as this is positive in up to 97% of polycythemia vera cases 1
The American Society of Hematology recommends confirming true erythrocytosis by repeating measurements, as single values are unreliable for diagnosis 1. However, with Hgb 17.8 g/dL and Hct 53.9%, this patient meets criteria for erythrocytosis (>16.5 g/dL in women or >18.5 g/dL in men for hemoglobin; >49.5% in women or >55% in men for hematocrit) 1.
Evaluate for Secondary Causes
Before assuming polycythemia vera, systematically exclude secondary causes:
- Smoking history and carbon monoxide exposure - "smoker's polycythemia" results from chronic tissue hypoxia stimulating erythropoietin production and resolves with cessation 1
- Sleep study if nocturnal symptoms present - obstructive sleep apnea produces nocturnal hypoxemia driving erythropoietin production 1
- Testosterone use (prescribed or unprescribed) - a common cause in younger adults that requires dose adjustment or discontinuation 1
- Chronic lung disease (COPD, chronic hypoxemia) - assess with pulse oximetry and pulmonary function tests if indicated 2
- Renal imaging if persistently elevated erythropoietin levels, to exclude renal cell carcinoma or other erythropoietin-producing tumors 2
Diagnosis of Polycythemia Vera
The World Health Organization criteria require:
- Major criteria: (1) Elevated hemoglobin/hematocrit AND (2) JAK2 mutation present 1
- Minor criteria: At least one of: aquagenic pruritus, splenomegaly, or erythromelalgia 1
Diagnosis is established with both major criteria plus one minor criterion, OR first major criterion plus two minor criteria 1.
Management Based on Diagnosis
If Polycythemia Vera is Confirmed:
Therapeutic phlebotomy to maintain hematocrit strictly below 45% is the cornerstone of treatment 3. This target significantly reduces thrombotic risk, which is the most lethal complication 3, 4.
Low-dose aspirin (100 mg daily) should be prescribed for all patients unless contraindicated, as it significantly reduces thrombotic events without substantially increasing bleeding risk 3.
Risk stratification determines need for cytoreductive therapy:
- High-risk patients (age ≥60 years, prior thrombosis, poor phlebotomy tolerance, symptomatic/progressive splenomegaly, platelets >1,500 × 10⁹/L, or progressive leukocytosis) require cytoreductive therapy 3
- First-line cytoreductive options: hydroxyurea, interferon alfa, or pegylated interferon 3
- Hydroxyurea is the most commonly used first-line agent but should be used cautiously in patients <40 years due to leukemogenic potential 3, 5
If Secondary Erythrocytosis:
Treatment targets the underlying condition:
- Smoking cessation for smoker's polycythemia 1
- CPAP therapy for obstructive sleep apnea 1
- Testosterone dose reduction or discontinuation if causative 1
- Management of chronic lung disease with appropriate pulmonary therapies 2
Critical Thresholds for Phlebotomy
Therapeutic phlebotomy is indicated ONLY when:
- Hemoglobin >20 g/dL AND hematocrit >65% with symptoms of hyperviscosity (headache, visual disturbances, dizziness) 1
- Dehydration has been excluded before proceeding 1
Your patient with Hgb 17.8 g/dL and Hct 53.9% does NOT meet criteria for immediate phlebotomy 1.
Important Phlebotomy Caveats:
Repeated routine phlebotomies are contraindicated due to risk of iron depletion, decreased oxygen-carrying capacity, and paradoxically increased stroke risk 2, 1. The American Heart Association specifically warns against aggressive phlebotomy in secondary erythrocytosis 2.
When phlebotomy is performed, replace with equal volume of saline or dextrose to prevent further hemoconcentration 1.
Iron Management Considerations
Iron deficiency commonly coexists with erythrocytosis and creates microcytic, rigid red cells with reduced oxygen-carrying capacity and deformability, increasing stroke risk 2, 1.
If iron deficiency is confirmed:
- Cautious oral iron supplementation with close hemoglobin monitoring is necessary, as rapid increases in red cell mass can occur 1
- Do not withhold iron replacement solely because of elevated hematocrit - iron-deficient red cells are more dangerous than iron-replete cells at the same hematocrit 2
Referral Indications
Immediate hematology referral is warranted for:
- Positive JAK2 mutation 1
- Hemoglobin >20 g/dL with hyperviscosity symptoms 1
- Unexplained splenomegaly 1
- Uncertainty in diagnosis or management 6
Common Pitfalls to Avoid
Do not perform aggressive phlebotomy based solely on elevated hematocrit - this causes iron depletion and increases thrombotic risk 2, 1.
Do not assume polycythemia vera without JAK2 testing - secondary causes are more common and require different management 1, 6.
Do not overlook coexisting iron deficiency - check ferritin and transferrin saturation in all cases, as MCV is unreliable 1.
Do not use hematocrit alone for monitoring - hemoglobin is more accurate and stable, as hematocrit can falsely increase with sample storage or hyperglycemia 1.