Management of Elevated Blood Cell Counts

Diagnostic Approach

The American College of Hematology recommends confirming true erythrocytosis with repeat measurements and complete diagnostic workup including JAK2 mutation testing, while simultaneously evaluating for secondary causes and assessing for hyperleukocytosis complications that may require urgent intervention 1
Repeat hemoglobin and hematocrit measurements are necessary to confirm true erythrocytosis, with diagnostic thresholds being hemoglobin >18.5 g/dL in men (>16.5 g/dL in women) or hematocrit >55% in men (>49.5% in women) 1
A complete blood count with differential should be ordered immediately to assess all three cell lines and examine for left shift or immature cells, particularly given the concurrent leukocytosis 2
Obtain peripheral blood smear review by a qualified hematologist to evaluate cell morphology, maturity, and rule out acute leukemia or other primary bone marrow disorders 1, 2

Test for JAK2 mutations (both exon 14 and exon 12) as the cornerstone diagnostic test, which is present in up to 97% of polycythemia vera cases 1
Measure serum ferritin, transferrin saturation, and iron levels to identify coexisting iron deficiency, which is common in erythrocytosis and causes microcytic polycythemia with elevated RBC count but reduced hemoglobin 1
Check reticulocyte count to evaluate bone marrow response 1
Measure C-reactive protein (CRP) as part of the minimum workup 1
Assess erythropoietin levels to differentiate primary from secondary causes 1

If white blood cell count exceeds 100,000/μL, initiate aggressive intravenous hydration at 2.5-3 liters/m²/day immediately to prevent tumor lysis syndrome and leukostasis complications 2
Monitor closely for leukostasis symptoms (respiratory distress, altered mental status, visual changes, priapism), which constitutes a medical emergency requiring potential leukapheresis 2
Consider starting hydroxyurea 50-60 mg/kg/day to achieve 50% WBC reduction within 1-2 weeks if hyperleukocytosis is present 2

Obtain detailed smoking history and assess for carbon monoxide exposure, as "smoker's polycythemia" results from chronic tissue hypoxia stimulating erythropoietin production and resolves with cessation 1
Screen for obstructive sleep apnea with sleep study if nocturnal hypoxemia is suspected, which produces erythropoietin-driven erythrocytosis 1
Evaluate for chronic obstructive pulmonary disease or other pulmonary conditions causing chronic hypoxemia 1
Assess for testosterone use (prescribed or unprescribed), which commonly causes erythrocytosis in young adults 1

Polycythemia vera diagnosis requires both major criteria (elevated hemoglobin/hematocrit/RBC mass AND JAK2 mutation) plus at least one minor criterion, OR first major criterion plus at least two minor criteria 1
Maintain hematocrit strictly below 45% through therapeutic phlebotomy to reduce thrombotic risk, as demonstrated by the CYTO-PV study 1
Initiate low-dose aspirin (81-100 mg daily) as the second cornerstone of therapy for thrombosis prevention 1

Use hemoglobin rather than hematocrit for ongoing monitoring, as hemoglobin remains stable during sample storage while hematocrit can falsely increase by 2-4% 1
Monitor hemoglobin levels weekly until any steroid tapering process is complete if immunosuppression is initiated 3
Avoid rapid increases in hematocrit (>8 percentage points per month) if erythropoietin therapy is involved 1