Optimal Phlebotomy Interval to Change Hematocrit Levels in Patients with Polycythemia

Abstract

BACKGROUND: Phlebotomy is used to maintain hematocrit levels <45% to prevent polycythemia-related thrombotic events. However, guidelines for the phlebotomy intervals are lacking. Therefore, we analyzed post-phlebotomy changes in hematocrit and determined the optimal phlebotomy intervals for patients with polycythemia. METHODS: Between March 2009 and August 2016, we performed 441 phlebotomies for 48 patients with polycythemia. Patients with high-risk polycythemia vera (PV) or secondary polycythemia with hypertension or arrhythmia were medicated with hydroxyurea. We divided the patients into three groups based on phlebotomy interval: <2 weeks, 2~4 weeks, and >4 weeks. RESULTS: No patients with secondary polycythemia and 25.8% of the patients with PV had thrombotic events pre-phlebotomy. Post-phlebotomy, none of the patients experienced a thrombotic event. The average decrease in hematocrit level was significantly different between the three groups, being 1.98±1.90% (<2 weeks), 0.73±2.53% (2~4 weeks), and −0.46±4.80% (>4 weeks). CONCLUSION: To prevent thrombotic events, phlebotomy is a safe and effective treatment to reduce hematocrit levels in patients with polycythemia, regardless of medication. For the maximum effect, a <2-week phlebotomy interval to reduce and <4-week phlebotomy interval to maintain hematocrit levels could be effective.