Diagnosis and Treatment of Essential Thrombocythemia: Assessment of Current Clinical Practice.
Authors: Lee Vivian H Y , Peterson Erica , Zypchen Leslie , Foltz Lynda M 
Published: October 2019

Abstract
Abstract 1903
Poster Board I-926

Introduction:
The discovery of the JAK2 V617F gene mutation has significantly altered the clinical diagnostic approach to the myeloproliferative neoplasms, reflected in the revised 2008 WHO diagnostic criteria. Both the 2001 and 2008 diagnostic criteria for essential thrombocythemia (ET) require a bone marrow biopsy showing megakaryocytic proliferation to make a diagnosis of ET. Published expert opinion based on clinical studies suggests that ET patients > 60 years old or with history of thrombosis should be characterized as high risk and treated with hydroxyurea. It is unclear whether physicians in clinical practice utilize the WHO diagnostic criteria or follow expert treatment recommendations for ET.

Methods:
We conducted a retrospective chart review of all patients with a clinical diagnosis of ET made by a hematologist who were seen in clinic from 2006 to 2008 at two university teaching hospitals in Vancouver, Canada. Data collected included demographic information, thrombosis history, diagnostic tests performed and treatment administered. Testing for JAK2 V617F became locally available in 2006, so for assessment of diagnostic tests performed, patients were divided into cohorts of diagnosis pre-2006 and 2006–2008. Patients were characterized as high risk if > 60 y or history of thrombosis at the time of diagnosis. All other patients were considered low risk.

Results:
Diagnostic information was available for 116 patients diagnosed prior to the availability of testing for JAK2 V617F. 65% (75/116) of patients in this cohort had a bone marrow biopsy performed (table 1). 44 patients received a new diagnosis of ET from 2006–2008. Only 48% (21/44) patients in this cohort had a bone marrow biopsy performed, significantly less than in the historical cohort (p = 0.019). 41/44 had JAK2 V617F testing performed: 41% (17/41) were JAK2 V617F negative, 56% (23/41) positive and 1 equivocal. Bone marrow biopsy was performed in 59% (10/17) of JAK2 V617F negative patients and 39% (9/23) of JAK2 V617F positive patients (p = 0.055) (table 1). Bone marrow biopsy was also performed in 1 patient with equivocal JAK2 V617F testing and 1 patient not tested for JAK2 V617F. 170 patients diagnosed with ET were seen in follow up 2006–2008. 64% (109/170) were high risk due to age > 60 y or history of thrombosis. The remaining 36% (61/170) were considered low risk. Hydroxyurea was used preferentially over anagrelide for treatment of ET (table 2). Only 76% of high risk patients were receiving cytoreductive treatment. 23% of low risk patients received cytoreductive treatment. ASA was prescribed to 89% of high risk and 79% of low risk patients.

Conclusion:
Despite the requirement for a bone marrow biopsy to meet the WHO criteria for ET, hematologists performed a bone marrow biopsy in less than half of patients they diagnosed with ET since 2006. Hematologists performed bone marrow biopsy less frequently after JAK2 V617F testing became available, particularly in JAK2 V617F positive patients. A substantial portion of high risk patients (24%) were receiving no cytoreductive therapy, contrary to expert recommendation. Further study is required to understand the barriers to implementing treatment recommendations in clinical practice. This study highlights the challenges in translating published diagnostic criteria and treatment guidelines into changes in patient care.

Disclosures:
No relevant conflicts of interest to declare.