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Essential ThrombocythemiaMANAGEMENT

HEMATOLOGIC AND ONCOLOGIC PRESENTATIONS · 12 SECTIONS

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795 items

☷ Legend

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Cardiovascular Presentations71▾

Respiratory Presentations52▾

Neurological Presentations83▾

Gastrointestinal Presentations74▾

Genitourinary and Reproductive Presentations48▾

Infectious Disease Presentations148▾

Trauma Presentations89▾

Toxicologic Presentations80▾

Psychiatric Presentations26▾

Musculoskeletal and Rheumatologic Presentations96▾

Dermatology Presentations23▾

Environmental and Exposure Presentations27▾

Hematologic and Oncologic Presentations36▾

Acute chest syndrome Acute Hemolytic Transfusion Reaction Anticoagulant reversal (warfarin, DOAC, heparin)Aplastic Anemia (Crisis)Autoimmune Hemolytic Anemia CAR-T and cytokine release syndrome Coagulopathy Delayed Hemolytic Transfusion Reaction Disseminated Intravascular Coagulation (DIC)Essential Thrombocythemia Febrile Non-hemolytic Transfusion Reaction Graft Versus Host Disease (Acute)Hemolytic Uremic Syndrome (HUS)Hemophilia A (Bleeding Crisis)Heparin-Induced Thrombocytopenia (HIT)Hyperviscosity syndrome Immune checkpoint inhibitor toxicity Immune Thrombocytopenic Purpura (ITP)Leukemoid Reaction Leukostasis Massive transfusion protocol Myelofibrosis Neutropenic enterocolitis (typhlitis)Paroxysmal Nocturnal Hemoglobinuria Polycythemia Vera (Crisis)Pure Red Cell Aplasia Sickle Cell (Acute Chest Syndrome)Sickle Cell (Splenic Sequestration)Sickle cell crisis (vaso-occlusive)Symptomatic anemia Thrombocytopenia (severe)Thrombotic Thrombocytopenic Purpura (TTP)Transfusion-Associated Circulatory Overload (TACO)Transfusion-Related Acute Lung Injury (TRALI)Tumor lysis syndrome Von Willebrand Disease (Bleeding)

Pediatric-Specific Presentations19▾

Endocrine and Metabolic Presentations45▾

ENT and Maxillofacial Presentations27▾

Ophthalmologic Presentations19▾

Obstetric Presentations23▾

Systemic and Miscellaneous Presentations17▾

01Approach to the Critical Patient/attcp43

Immediate priorities

›Acute thrombotic event recognition

›Arterial thrombosis presentations

›Acute stroke or TIA symptoms

›Acute coronary syndrome with ST changes

›Digital ischemia or limb threatening ischemia

›Venous thrombosis presentations

›Splanchnic vein thrombosis with abdominal pain

›Cerebral venous sinus thrombosis with headache

›Pulmonary embolism with dyspnea and hypoxemia

›If acute arterial thrombosis, activate stroke or STEMI pathway as indicated

›Platelet count does not preclude reperfusion in ACS

›Hematology emergency consultation for antiplatelet and anticoagulation strategy

›Hemorrhagic emergency assessment

›Active major bleeding

›GI hemorrhage with hemodynamic instability

›Intracranial hemorrhage

›Hemorrhagic stroke as emergency imaging trigger

›Acquired von Willebrand syndrome risk

›Platelet count >1,000 x 10^9/L as key threshold

›VWF activity <30% confirms diagnosis

›If active major bleeding with suspected acquired VWS, withhold aspirin

›Platelet pheresis for extreme thrombocytosis with life-threatening hemorrhage

›Hematology and transfusion medicine consultation

Monitoring and targets

›Hemodynamic monitoring

›Continuous cardiac monitoring for arrhythmia and ischemia

›ST changes as thrombotic event trigger

02History/hx91

Presentation pattern

›Microcirculatory symptoms

›Erythromelalgia

›Burning pain with erythema and warmth in distal extremities

›Triggered by warmth or exercise

›Acral paresthesias

›Tingling or burning in fingers and toes

›Hands and feet predominant distribution

›Headache and neurologic symptoms

›Dizziness and lightheadedness

›Visual disturbances including scotomata and blurred vision

›Thrombotic event symptoms

›Arterial events

›Focal neurologic deficit or TIA symptoms

›Chest pain or pressure consistent with ACS

›Limb pain with pallor or absent pulse

›Venous events

›Unilateral leg swelling and pain for DVT

›Abdominal pain especially postprandial for splanchnic thrombosis

›Acute severe headache for cerebral venous thrombosis

›Hemorrhagic symptoms

›Mucocutaneous bleeding

›Epistaxis

›Gum bleeding

›Easy bruising

›GI bleeding

›Hematemesis or melena

›Association with extreme thrombocytosis

›Menorrhagia in reproductive age females

Incidental diagnosis context

›Asymptomatic discovery

›Routine CBC abnormality

›Over 50% of ET diagnosed incidentally

›Persistent platelet count >=450 x 10^9/L trigger

›Chronicity of platelet elevation

›Prior CBC values for trajectory

›Duration of elevation

Risk factors and history

›Thrombosis risk factors

›Age >60 years

›Independent predictor in revised IPSET-Thrombosis

›Risk increases with additional cardiovascular factors

›Prior thrombotic event

›Strongest single predictor of recurrent thrombosis

›Arterial and venous events both count

›JAK2 V617F mutation status

›Associated with higher arterial and venous thrombosis rates

›Present in approximately 55% of ET cases

›Cardiovascular risk factors

›Hypertension

›Diabetes mellitus

›Hyperlipidemia

›Active tobacco use

›Hemorrhage risk factors

›Extreme thrombocytosis

›Platelet count >1,000 to 1,500 x 10^9/L

›Acquired VWS mechanism

›Prior hemorrhagic events

›GI bleed history

›Mucocutaneous bleeding pattern

›Disease transformation risk

›Constitutional symptoms

›Weight loss >10% in 6 months

›Drenching night sweats

›Unexplained fever >37.5 degrees C

›Duration of disease

›10% develop post-ET myelofibrosis at median 8.5 years

›3% develop acute myeloid leukemia over time

Medications and prior treatment

›Current antiplatelet and anticoagulant use

›Low-dose aspirin use and dose

›Once or twice daily dosing

›Indication and tolerance

›Anticoagulant therapy

›Anticoagulant type and duration

›Indication for anticoagulation

›Cytoreductive therapy history

›Hydroxyurea use and response

›Current dose and tolerability

›Platelet count response

›Interferon or anagrelide use

›Prior treatments and reasons for change

›Adherence and side effects

Family and social history

›Family history

›Myeloproliferative neoplasms in first degree relatives

›Rare familial clustering exists

›Hereditary thrombocytosis syndromes consideration

›Thrombotic or hemorrhagic history in family

›Social history

›Smoking status

›Modifiable cardiovascular risk factor

›Quantify pack-year history

›Occupation and activity level

›Prolonged immobility risk

›Dehydration exposure

03Physical Exam/exam60

Vital signs and general

›Hemodynamic assessment

›Blood pressure

›Hypertension documentation as cardiovascular risk modifier

›Hypotension as hemorrhagic or thrombotic emergency marker

›Heart rate

›Tachycardia in PE or hemorrhage

›Rate in ACS context

›Temperature

›Fever suggesting disease transformation

›Constitutional symptom documentation

›Oxygen saturation

›Desaturation in pulmonary embolism or hemorrhage

›Room air baseline

Abdominal exam

›Splenomegaly assessment

›Palpable spleen

›Present in approximately 12% at diagnosis

›Measure in cm below costal margin

›Hepatomegaly

›Less common than splenomegaly

›Assess for splanchnic thrombosis tenderness

›Abdominal tenderness

›RUQ tenderness in portal or hepatic vein thrombosis

›Diffuse tenderness in mesenteric ischemia

Skin and extremity exam

›Erythromelalgia signs

›Distal extremity erythema and warmth

04Differential Diagnosis/ddx48

Thrombocytosis differential

›Reactive thrombocytosis

›Most common cause accounting for 85 to 90% of thrombocytosis

›Infection and inflammatory states

›Iron deficiency anemia

›Post-splenectomy state

›Solid tumors

›Recovery from chemotherapy or alcohol use

›Key distinguishing features

›Transient course with underlying cause

›Absence of driver mutations

›Other myeloproliferative neoplasms

›Polycythemia vera

›ICD-10 D45

›Elevated hemoglobin and hematocrit

›JAK2 exon 12 mutations possible

›Prefibrotic primary myelofibrosis

›ICD-10 D47.4

›Bone marrow morphology distinguishes

›Atypical megakaryocytes and reticulin fibrosis

›Chronic myeloid leukemia

›ICD-10 C92.10

›BCR::ABL1 fusion mandatory exclusion

›Leukocytosis with left shift more prominent

›Myelodysplastic myeloproliferative overlap syndromes

›ICD-10 D46 range

›Dysplastic features on marrow

›Other conditions

05Laboratory Tests/lt73

Diagnostic workup labs

›Complete blood count with differential

›Platelet count

›Persistent >=450 x 10^9/L required for diagnosis

›Morphology on smear for large or hypogranular platelets

›White blood cell count and differential

›Leukocytosis with left shift suggests CML or MF

›Leukoerythroblastic smear suggests fibrotic transformation

›Hemoglobin and red cell indices

›Elevated hemoglobin points to PV

›Microcytic anemia suggests iron deficiency reactive cause

›Molecular testing

›JAK2 V617F mutation

›First-line molecular test

›Present in approximately 55% of ET

›CALR mutation testing

›If JAK2 negative

›Present in approximately 25% of ET

›MPL mutation testing

›If JAK2 and CALR negative

›Present in approximately 3% of ET

›BCR::ABL1 FISH or RT-PCR

›Mandatory exclusion of CML

›Negative result required before ET diagnosis

›Iron studies

›Serum ferritin

›Low ferritin confirms iron deficiency as reactive cause

›Normal or elevated supports primary process

06Diagnostic Tests/dt85

Scoring Systems

›Revised IPSET-Thrombosis risk stratification

›Very-low risk

›Age <=60 years

›No prior thrombosis

›JAK2 negative

›No cardiovascular risk factors

›Management: observation or aspirin if CV risk factors borderline

›Low risk

›Age <=60 years

›No prior thrombosis

›JAK2 positive or cardiovascular risk factors present

›Management: aspirin 81-100 mg daily

›Intermediate risk

›Age >60 years

›No prior thrombosis

›JAK2 negative

›Management: aspirin and cytoreduction controversial

›High risk

›Prior thrombosis at any age

›Or age >60 with JAK2 mutation

›Management: cytoreduction plus aspirin

›MPN Symptom Assessment Form Total Symptom Score

›Standardized symptom burden tool

›Recommended by NCCN v1.2026

›10 symptom domains scored 0 to 10

›Clinical utility

›Baseline and treatment response tracking

›Fatigue, pruritus, night sweats, bone pain, abdominal discomfort, concentration

MRI

›MRI applications in ET complications

›Brain MRI and MRV

›Cerebral venous sinus thrombosis confirmation

›Silent cerebral infarcts in ET patients with neurologic symptoms

›MRI abdomen with MRV

›Portal vein, hepatic vein, and mesenteric vein thrombosis evaluation

›Budd-Chiari syndrome characterization

›Bone marrow MRI

›Hypercellular marrow pattern in myeloproliferative disease

›Fibrotic transformation signal changes

›Limitations

›Availability in acute setting

›Non-compatible implants contraindication

›CT angiography for thrombosis

›Splanchnic CT angiography

›Portal, mesenteric, hepatic, and splenic vein thrombosis detection

›Bowel ischemia assessment

›CT pulmonary angiography

›Pulmonary embolism diagnosis

›Sensitivity >95% and specificity >95%

›CT head without contrast

›Acute hemorrhagic stroke exclusion

›First imaging step before MRI for acute neurologic presentation

›CT chest abdomen pelvis

›Spleen and liver size measurement

›More accurate than clinical examination

›Baseline and progression monitoring

›Lymphadenopathy assessment

›Transformation features

›Differential diagnosis support

›Contrast considerations

›Renal function assessment before contrast

›Allergy premedication when indicated

Ultrasound

›Abdominal ultrasound

›Spleen size measurement

›Longitudinal diameter in cm

›Serial measurements for progression monitoring

›Portal vein Doppler

›Portal flow direction and velocity

›Portal vein thrombosis screening

›Hepatic vein Doppler

›Hepatic vein patency for Budd-Chiari assessment

›Triphasic waveform absence as thrombosis marker

›Extremity Doppler ultrasound

›DVT assessment

›Compressibility loss in thrombosed segments

›Sensitivity and specificity >95% for proximal DVT

›Arterial Doppler

›Ankle brachial index in peripheral arterial thrombosis

›Digital artery assessment in severe erythromelalgia

›POCUS applications

›Cardiac function assessment

›LV function estimation in hemodynamic compromise

›RV strain in massive PE

›IVC assessment

›Volume status and fluid responsiveness adjunct

›Limitations in spontaneously breathing patients

07Disposition/dispo45

Risk stratification for admission

›Admission indications

›Acute thrombotic event

›Stroke or TIA requiring anticoagulation initiation

›ACS requiring antiplatelet and anticoagulation strategy

›Splanchnic vein thrombosis with hemodynamic concern

›Active hemorrhage

›GI bleed requiring endoscopy or transfusion

›Intracranial hemorrhage

›Disease-related emergency

›Extreme thrombocytosis with acquired VWS

›Suspected blast transformation with constitutional symptoms

›New diagnosis requiring workup

›Bone marrow biopsy coordination

›Molecular testing and subspecialty referral

Level of care criteria

›ICU indications

›Hemodynamic instability

›Hemorrhagic shock requiring resuscitation

›Cardiogenic shock from ACS with platelet count elevation

›Major thrombotic event with instability

›Massive PE with right heart strain

›Large territory ischemic stroke with elevated ICP

›Platelet pheresis requirement

›Life-threatening hemorrhage with extreme thrombocytosis

›Requires monitoring and access

›Hematology ward or step-down

›Stable thrombotic event after initial management

08Treatment/t121

Antiplatelet therapy

›Low-dose aspirin

›Dosing

›81 to 100 mg orally daily

›Twice daily aspirin 81 mg for refractory microvascular symptoms

›Indications

›Low, intermediate, and high risk ET

›Very-low risk with cardiovascular risk factors

›Contraindications

›Active major bleeding

›Acquired VWS with VWF activity <30%

›Platelet count >1,000 x 10^9/L without VWF testing

›Evidence

›Class I recommendation for most ET patients

›Reduces microvascular symptom burden

Cytoreductive therapy

›Hydroxyurea

›Indication

›High-risk ET first-line cytoreduction

›Age >60 with JAK2 and prior thrombosis

›Dosing

›Starting dose 500 to 1,000 mg orally daily

›Titrate to platelet count <400 x 10^9/L

›Monitoring

›CBC every 2 to 4 weeks during titration

›Mouth sores and leg ulcers as adverse effects

›Contraindications

›Pregnancy due to teratogenicity

›Avoid in reproductive age patients if alternatives available

›Evidence

›Class I recommendation for high-risk ET per NCCN v1.2026

›Peginterferon alfa-2a

›Indication

›Preferred for younger patients and those deferring hydroxyurea

›Preferred in pregnancy-planning patients

›Dosing

›45 to 180 mcg subcutaneously weekly

›Titrate based on response and tolerability

›Adverse effects

›Flu-like symptoms

›Depression screening required

›Autoimmune activation

›Evidence

›Category 1 option per NCCN for younger patients

›Ropeginterferon alfa-2b-njft

›Indication

›Second-line inadequate or loss of response to prior therapy

›Category 1 preferred second-line per NCCN v1.2026

›Dosing

›100 mcg subcutaneously every 2 weeks initially

›Titrate to response up to 500 mcg every 2 weeks

›Monitoring

›CBC and LFTs during therapy

›Thyroid function every 6 months

›Anagrelide

›Indication

›Alternative second-line cytoreductive option

›Useful in certain circumstances per NCCN v1.2026

›Dosing

›0.5 mg orally twice daily initial dose

›Increase by 0.5 mg per week maximum

›Target platelet count <600 x 10^9/L

›Adverse effects

›Palpitations and fluid retention

›Cardiotoxicity risk

›Avoid in cardiac disease

›Ruxolitinib

›Indication

›Refractory ET not responding to prior cytoreduction

›Useful in certain circumstances per NCCN

›Dosing

›5 to 10 mg orally twice daily

›Dose adjust for cytopenias and renal function

›Monitoring

›CBC and metabolic panel

›Infection risk including herpes zoster

Anticoagulation for thrombosis

›Acute thrombotic event anticoagulation

›Low molecular weight heparin

›Enoxaparin 1 mg/kg subcutaneously every 12 hours

›Renal adjustment for CrCl <30 mL/min

›Preferred for initial therapy in most settings

›Unfractionated heparin IV

›Weight-based bolus 80 units/kg then 18 units/kg/hour

›aPTT target 60 to 100 seconds

›Used when rapid reversal may be needed

›Transition to oral anticoagulation

›Warfarin with INR target 2.0 to 3.0 for VTE

›DOACs as alternative with hematology guidance

›Splanchnic vein thrombosis management

›Indefinite anticoagulation often required

›High recurrence risk with underlying MPN

›Duration guided by hematology

›Cytoreduction in parallel

›Platelet count control as adjunctive measure

›Thrombotic risk reduction

Management of acquired VWS

›Extreme thrombocytosis with bleeding

›VWF activity assessment first

›VWF activity <30% confirms acquired VWS

›Withhold aspirin while bleeding active

›Cytoreduction to lower platelet count

›Platelet count reduction resolves acquired VWS

›Hydroxyurea rapid effect within days to weeks

›Platelet pheresis for emergency

›Life-threatening hemorrhage with platelet count >1,500 x 10^9/L

›Bridge to cytoreduction

›DDAVP use limited

›May be considered for acute bleeding episodes

›Tachyphylaxis limits repeated dosing

Erythromelalgia treatment

›Low-dose aspirin

›Highly effective for erythromelalgia

›Relief often within 24 to 48 hours

›Twice daily dosing for refractory cases

›Mechanism

›COX-1 inhibition preventing platelet thromboxane

›Reduces platelet-mediated microvascular occlusion

›Cooling measures

›Symptom relief adjunct

›Cool water immersion for acute episodes

›Avoid heat triggers

›Cytoreduction if aspirin insufficient

›Platelet count reduction improves symptoms

›Target platelet count <400 x 10^9/L

›Hydroxyurea or interferon as options

09Special Populations/sp59

Pregnancy

›Pregnancy in ET

›Risk profile

›Elevated miscarriage risk particularly in first trimester

›Placental infarction and growth restriction risk

›Maternal thrombosis and hemorrhage risk

›Cytoreductive therapy in pregnancy

›Hydroxyurea strictly contraindicated due to teratogenicity

›Peginterferon alfa-2a preferred cytoreductive agent

›Anagrelide not recommended in pregnancy

›Aspirin in pregnancy

›Low-dose aspirin generally continued throughout pregnancy

›Benefits outweigh risks in most risk categories

›LMWH anticoagulation

›Enoxaparin preferred for anticoagulation in pregnancy

›Warfarin and DOACs contraindicated

›Monitoring

›High-risk obstetric care with maternal fetal medicine

›Serial fetal growth ultrasound each trimester

›CBC monthly during pregnancy

Geriatric

›Older adult considerations

›Higher thrombosis baseline risk

›Age >60 is independent risk factor in IPSET

›Cardiovascular comorbidities often present

›Hydroxyurea tolerability

›Preferred first-line cytoreduction in older patients

›Renal function monitoring required

10Background/b88

Epidemiology

›Incidence and prevalence

›Annual incidence approximately 1.5 per 100,000 persons in the United States

›Female predominance in younger patients

›Male predominance in older patients

›Median age at diagnosis 59 years

›Bimodal distribution with second peak in young women aged 30 to 40

›Asymptomatic discovery common

›Prevalence estimated 10 to 30 per 100,000

›Long natural history contributes to high prevalence relative to incidence

›Prognosis and survival

›Median overall survival exceeds 35 years when diagnosed at age <=40

›Normal or near-normal life expectancy in young patients

›Reduced life expectancy with transformation

›Transformation rates

›Approximately 10% develop post-ET myelofibrosis at median 8.5 years

›Approximately 3% develop acute myeloid leukemia

›Major complication rates

›Arterial thrombosis 11%

›Venous thrombosis 7%

›Hemorrhagic complications 8%

Pathophysiology

›Clonal origin

›Myeloproliferative neoplasm arising from pluripotent hematopoietic stem cell

›Clonal proliferation of megakaryocyte lineage

›WHO 2022 classification as MPN category

›Diagnostic criteria platelet count >=450 x 10^9/L persistent

›With megakaryocyte proliferation on marrow

›Exclusion of other causes

›Driver mutations

›JAK2 V617F

›Present in approximately 55% of ET

›Activates JAK-STAT signaling pathway

›Associated with higher thrombosis and erythrocytosis tendency

›CALR mutations

›Present in approximately 25% of ET

›Exon 9 insertions or deletions

›Activates MPL signaling via CALR-MPL interaction

›MPL mutations

›Present in approximately 3% of ET

›Activates thrombopoietin receptor

›Associated with anemia and splenomegaly

›Triple-negative ET

›Approximately 12 to 15% lack JAK2, CALR, MPL mutations

›NGS panels to establish clonality

›Thrombosis mechanism

›Platelet activation and aggregation

›Quantitative excess and qualitative defects

›Increased platelet-leukocyte aggregate formation

›Erythromelalgia mechanism

›Platelet-mediated microvascular occlusion

›Thromboxane A2 release

›COX-1 mediated and aspirin-sensitive

›Hemorrhage mechanism

›Acquired von Willebrand syndrome

›High-molecular-weight VWF multimers adsorbed to platelet surface

›Proteolytic degradation by ADAMTS13 on enlarged platelet surface

›Platelet count >1,000 to 1,500 x 10^9/L threshold

Therapeutic Considerations

›Risk stratification guides treatment intensity

›Revised IPSET-Thrombosis model

›Very-low risk: observation or aspirin only

›Low risk: aspirin 81 to 100 mg daily

›High risk: aspirin plus cytoreduction

›No treatment has been shown to prevent transformation to MF or AML

›Cytoreduction goal is thrombosis prevention

›Surveillance for progression is ongoing need

›Aspirin evidence base

›Reduces microvascular symptom burden including erythromelalgia

›Class I recommendation for most patients

›Twice daily effective for refractory symptoms

›Bleeding risk must be balanced

›Avoid in acquired VWS

›Avoid with active bleeding

›Cytoreduction therapy selection

›Hydroxyurea preferred in high-risk older patients

›Reduces thrombotic events in high-risk ET

›NCCN Category 1 for high-risk patients

›Interferon preferred in younger patients and pregnancy planning

›No teratogenicity

›Molecular response possible

›Anagrelide as alternative

›Platelet-specific reduction without total WBC effect

›Cardiac side effects limit use in older patients

›Perioperative management

›Elective surgery risk elevated in MPN

›Platelet count reduction to <400 x 10^9/L before elective surgery

›Aspirin held 7 days before surgery if clinically safe

›Anticoagulation bridging individualized

›High thrombosis risk requires bridging

›Hemorrhage risk assessment with VWF testing

11Patient Discharge Instructions/pdi46

copy discharge instructions

›Essential thrombocythemia home care instructions

›Take all medications exactly as prescribed

›Low-dose aspirin daily unless told to stop

›Cytoreductive medication at same time each day

›Stay well hydrated

›At least 2 liters of water daily

›Avoid dehydration which increases blood viscosity

›Protect feet and hands from heat

›Erythromelalgia triggered by warmth

›Cool water soaks for symptom relief

›Avoid smoking

›Tobacco significantly increases thrombosis risk

›Cessation resources available

›Warning signs requiring immediate return to emergency department

›Sudden severe headache or worst headache of life

›May indicate cerebral venous thrombosis or hemorrhage

›Sudden weakness or numbness in face arm or leg

›May indicate stroke or TIA

›Chest pain or shortness of breath

›May indicate heart attack or pulmonary embolism

›Severe abdominal pain especially upper abdomen

›May indicate splanchnic vein thrombosis

›Significant bleeding

›Heavy nosebleed not stopping with pressure

›Blood in stool or black tarry stool

›Heavy menstrual bleeding

›Burning red painful feet or hands that are severe

12References/r36

Guidelines and key sources

›NCCN Clinical Practice Guidelines in Oncology

›Myeloproliferative Neoplasms v1.2026

›Risk stratification and treatment algorithms

›Category 1 and 2A recommendations for ET

›Available at NCCN.org for registered users

›WHO Classification of Haematolymphoid Tumours 2022

›Essential thrombocythemia diagnostic criteria

›Platelet count threshold and morphologic criteria

›Exclusion criteria for other MPNs

›Revised IPSET-Thrombosis model

›Barbui T et al. Blood 2012 and subsequent validation studies

›Four-tier risk classification system

›Guides cytoreduction and antiplatelet decisions

Key trials and evidence

›Landmark cytoreduction trials

›PT-1 trial hydroxyurea vs anagrelide

›Hydroxyurea superior to anagrelide in high-risk ET

›Reduced arterial thrombosis and hemorrhage rates

›Interferon trials including PROUD and CONTINUATION studies

›Molecular response rates with interferon

›Non-inferior to hydroxyurea for thrombosis prevention

›Acquired VWS evidence

›Coagulation studies establishing VWF activity threshold

›VWF activity <30% associated with hemorrhage risk

›Platelet count >1,000 x 10^9/L as screening threshold

Coding and classification

›ICD-10 coding

Learn More: Essential Thrombocythemia→

Comprehensive Clinical Review

Structured, evidence-informed, long-form analysis for deeper understanding.

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed August 18, 2026

SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.