What is the typical initial therapy goal in polycythemia vera to reduce thrombosis risk?

• A. WBC normalization
• B. Hematocrit <45%
• C. Platelet count normalization
• D. Hemoglobin normalization

Answer: (B)

In polycythemia vera, the biggest risk for thrombosis comes from increased blood viscosity due to excess red blood cells. The most effective initial goal is to lower that viscosity by reducing the red cell mass, which is done by keeping the hematocrit below 45%. Phlebotomy is commonly used to reach this target, and achieving a hematocrit under 45% directly lowers thrombotic risk by improving blood flow and reducing viscosity. Hemoglobin levels tend to fall as hematocrit is reduced, but the specific target is hematocrit because it best reflects the actual red cell mass driving viscosity. While aspirin is added to decrease platelet aggregation and cytoreductive therapy may be needed for high-risk patients, the primary early objective to reduce thrombosis risk is maintaining hematocrit below 45%.