Goal Hemoglobin and Parameters for Therapeutic Phlebotomy in Polycythemia Vera
The primary goal of therapeutic phlebotomy in polycythemia vera is to maintain hematocrit below 45% in all patients, which has been definitively shown to reduce thrombotic risk. 1, 2
Target Hematocrit Level
Maintain hematocrit <45% for all patients with PV, regardless of sex. This target is based on evidence demonstrating significantly reduced thrombotic events when this threshold is maintained. 3, 1, 2, 4
The American Society of Hematology specifically recommends therapeutic phlebotomy to keep hematocrit below 45%, as this approach significantly reduces thrombotic risk. 1
Some older literature suggested sex-specific targets (hematocrit <42% for women and <45% for men), but current consensus favors the universal <45% target for both sexes. 5
Corresponding Hemoglobin Goals
While hematocrit is the primary parameter monitored for phlebotomy targets, the corresponding hemoglobin levels would be:
Hemoglobin should be maintained well below the diagnostic thresholds (which are >16.5 g/dL in men and >16.0 g/dL in women). 3, 2
The hematocrit target of <45% typically corresponds to hemoglobin levels of approximately <15 g/dL, though hematocrit remains the preferred monitoring parameter. 3, 4
Phlebotomy Technique and Frequency
Perform phlebotomy aggressively and periodically to achieve and maintain the hematocrit target. 3, 1
The rate and frequency of phlebotomy should be adjusted based on individual patient tolerance, as rapid phlebotomy rates have been identified as a risk factor for thrombosis. 5
Continue phlebotomy as the backbone of treatment for all patients with PV, regardless of risk category. 4, 6
Critical Caveats
Iron deficiency commonly develops with repeated phlebotomy and may mask the true degree of polycythemia by lowering hemoglobin/hematocrit levels. Monitor iron status but do not routinely supplement, as iron deficiency helps control erythrocytosis. 7
The <45% hematocrit target applies to all patients, not just high-risk individuals. This represents a shift from older practices that sometimes used higher targets in low-risk patients. 1, 2, 4
Phlebotomy alone is insufficient for high-risk patients (age >60 years or prior thrombosis history), who also require cytoreductive therapy with hydroxyurea or interferon-α in addition to maintaining the hematocrit target. 1, 4, 6
Adjunctive Therapy
All patients should receive low-dose aspirin (81-100 mg daily) unless contraindicated, as this significantly reduces thrombotic events without substantially increasing bleeding risk. 1, 2, 4
Avoid aspirin if platelet count exceeds 1,500 × 10⁹/L due to acquired von Willebrand disease risk and increased bleeding. 2, 5