The following article features coverage from the 61st American Society of Hematology Annual Meeting and Exposition. Click here to read more of Hematology Advisor’s conference coverage.

Treatment with aspirin and anticoagulation may lead to increased risk for hemorrhage in patients with polycythemia vera, according to results from the prospective phase 3 REVEAL study ( Identifier: NCT02252159) presented at the 61st American Society of Hematology (ASH) Annual Meeting in Orlando, Florida.

Researchers enrolled 2510 patients with polycythemia vera who had received aspirin (59.4%), anticoagulation treatment (7.2%), both (4.0%), or neither (29.3%). Warfarin (7.0%), rivaroxaban (2.1%), and apixaban (0.8%) were the most commonly prescribed anticoagulants at enrollment. Hypertension was reported in 56.0% of patients, and a history of thrombotic events was reported in 19.9% of patients. Outcomes included incidence of bleeding events and time to first hemorrhagic event.

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Hemorrhagic events occurred in 110 patients during a median follow-up of 2.3 years, most commonly in gastrointestinal and genitourinary sites. At least 1 severe hemorrhage was reported by 46 patients, with 38 patients requiring hospitalization and 7 patients experiencing fatal hemorrhage. Severe hemorrhage developed most commonly in gastrointestinal and central nervous system sites.

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Patients who received aspirin in combination with anticoagulation were found to experience a more than 3-fold increase in risk for severe hemorrhage (hazard ratio [HR], 3.31; P =.03) and more than a 4-fold increase in risk for hemorrhage overall (HR, 4.22; P <.0001) compared with patients receiving monotherapy or no therapy.

Extreme platelet counts (less than 100 x 109/L or more than 600 x 109/L) were found to be associated with increased hemorrhage risk in the overall cohort, with low platelet counts conferring a 4-fold risk and high platelet counts conferring a 2-fold risk. However, hemorrhage risk with anticoagulation and aspirin was independent of platelet count, with an adjusted HR of 4.18. Risk for severe hemorrhage was similarly independent of platelet count, with an adjusted HR of 3.48 (P =.006).

“Based on the observed 3-fold increased risk for severe hemorrhage associated with the combinations of an anticoagulant and aspirin, caution is advised when administering an antiplatelet agent with an anticoagulant in patients with polycythemia vera,” concluded Jeffrey I Zwicker, MD, of Beth Israel Deaconess Medical Center at Harvard Medical School in Boston, Massachusetts, during his presentation.

Disclosures: Some authors have declared affiliations with the pharmaceutical industry. Please refer to the original study for a full list of disclosures.


  1. Zwicker JI, Lessen DS, Colucci P, Paranagama D, Grunwald MR. Risk of hemorrhage in patients with polycythemia vera exposed to aspirin in combination with anticoagulants: results of a prospective, multicenter, observational cohort study (REVEAL). Oral presentation at: 61st ASH Annual meeting and Exposition; December 7-10, 2019; Orlando, FL. Abstract 168.