The Rate of Progression to Polycythemia Vera or Essential Thrombocythemia in Patients with Erythrocytosis or Thrombocytosis

The Rate of Progression to Polycythemia Vera or Essential Thrombocythemia in Patients with Erythrocytosis or Thrombocytosis

From S. Bortolo Hospital, Vicenza, Italy.

Abstract

Background: The clinical relevance of mild erythrocytosis (hematocrit > 0.48 in women or > 0.51 in men) or thrombocytosis (platelet count > 400 × 10⁹ cells/L) in asymptomatic persons is uncertain.

Objective: To estimate the frequency of polycythemia vera or essential thrombocythemia in persons with erythrocytosis or thrombocytosis in a general population.

Design: Cohort study.

Setting: Vicenza, Italy.

Participants: 10 000 community dwellers age 18 to 65 years and enrolled in the Vicenza Thrombophilia and Atherosclerosis project.

Measurements: Platelet count and hematocrit at baseline in all participants and at second follow-up if baseline results were abnormal. Measurement of erythrocyte sedimentation rate, peripheral arterial saturation, serum erythropoietin level, and leukocyte alkaline phosphatase level; chest radiography; abdominal ultrasonography; and occult fecal blood testing were done in persons with confirmed high hematocrit or platelet counts. Polycythemia vera and essential thrombocythemia were diagnosed according to the Polycythemia Study Group criteria.

Results: At baseline examination, 1 person had polycythemia vera, 1 had essential thrombocythemia, 88 had erythrocytosis, and 99 had thrombocytosis. Second examination confirmed erythrocytosis in 40% (95% CI, 29% to 51%) and thrombocytosis in 8% (CI, 4% to 15%) of those with abnormal baseline results. Among persons with confirmed abnormalities, further evaluation revealed 11 with idiopathic erythrocytosis, 2 with polycythemia vera (3/10 000 [CI, 0.6 to 8.7/10 000]), and 3 with essential thrombocythemia (4/10 000 [CI, 1.09 to 10.2/10 000]). After 5 years of follow-up, 1 additional person with a high platelet count developed essential thrombocythemia, and no persons developed hemorrhagic or thrombotic complications.

Conclusions: The prevalences of polycythemia vera and essential thrombocythemia were higher than expected in this general population. However, the risks for developing polycythemia vera, essential thrombocythemia, or associated vascular complications in persons with erythrocytosis or thrombocytosis were low.

Article and Author Information

Acknowledgments: The authors thank the field investigators, secretaries, nurses, and laboratory technicians who worked with us. They especially thank the family doctors of the town of Vicenza for their enthusiastic collaboration.
Grant Support: By grants from Fondazione Cassa di Risparmio di Verona, Vicenza, Belluno, ed Ancona; ALT (Associazione per la Lotta alla Trombosi), Milan; and AVEC (Associazione Veneta per l'Emofilia e le Coagulopatie), Vicenza, Italy.
Potential Financial Conflicts of Interest: None disclosed.
Requests for Single Reprints: Francesco Rodeghiero, MD, Department of Hematology, S. Bortolo Hospital, 36100 Vicenza, Italy; e-mail, rodeghiero{at}hemato.ven.it
Current Author Addresses: Drs. Ruggeri, Tosetto, Frezzato, and Rodeghiero: Department of Hematology, S. Bortolo Hospital, via Rodolfi, 37, 36100 Vicenza, Italy.
Author Contributions: Conception and design: M. Ruggeri, A. Tosetto.
Analysis and interpretation of the data: M. Ruggeri, A. Tosetto.
Drafting of the article: M. Ruggeri, A. Tosetto, F. Rodeghiero.
Critical revision of the article for important intellectual content: M. Ruggeri, A. Tosetto, F. Rodeghiero.
Final approval of the article: M. Ruggeri, A. Tosetto, F. Rodeghiero.
Provision of study materials or patients: M. Frezzato.
Statistical expertise: A. Tosetto.
Obtaining of funding: F. Rodeghiero.
Administrative, technical, or logistic support: M. Frezzato.
Collection and assembly of the data: M. Frezzato.