When should a patient with thrombocytosis (elevated platelet count) be referred to a hematologist?

Hematology Referral for Persistent Thrombocytosis

Refer patients with persistent thrombocytosis to a hematologist urgently (within 24-72 hours) if they have symptomatic disease, thrombotic events, microvascular symptoms, bleeding complications, or suspected primary thrombocytosis (myeloproliferative neoplasm). 1

Immediate/Urgent Referral Criteria (24-72 hours)

Refer immediately for any of the following:

• Symptomatic thrombocytosis with microvascular symptoms (headache, visual disturbances, erythromelalgia, paresthesias) 1
• Thrombotic or bleeding events at any platelet count 1
• Platelet count >1,000 × 10⁹/L (extreme thrombocytosis), which carries higher risk of complications regardless of etiology 1, 2
• Suspected primary/clonal thrombocytosis (myeloproliferative neoplasm), which accounts for 12.5% of thrombocytosis cases and has significantly higher complication rates (17.1% vs 7.9% for secondary causes) 1, 2
• Pregnancy with suspected myeloproliferative neoplasm, requiring specialized interferon-alpha management 1

Standard Referral Criteria

Refer for hematology evaluation if:

• Persistent unexplained thrombocytosis that remains elevated after treating secondary causes 3
• Platelet count persistently >700 × 10⁹/L (moderate thrombocytosis), even if asymptomatic, to exclude primary causes 3
• Paradoxical bleeding with very high platelets (>1,500 × 10⁹/L), suggesting acquired von Willebrand syndrome 1
• Splenomegaly with thrombocytosis, which suggests primary myeloproliferative disorder 4
• Qualitative platelet abnormalities on blood smear review 4

Risk Stratification While Awaiting Consultation

For patients with cardiovascular risk factors or JAK2 mutation:

• Consider low-dose aspirin (81-100 mg daily) if platelet count <1,500 × 10⁹/L 1
• Avoid aspirin if platelets >1,500 × 10⁹/L due to acquired von Willebrand syndrome risk 1
• Aggressively manage hypertension, diabetes, hyperlipidemia, and smoking 1

Outpatient Monitoring Acceptable When:

• Secondary/reactive thrombocytosis with identified cause (infection, inflammation, iron deficiency, malignancy, tissue damage, post-splenectomy) 3
• Mild thrombocytosis (500-700 × 10⁹/L) that is asymptomatic with clear reactive etiology 3
• Patient has no bleeding symptoms, no thrombotic events, and no arterial disease 5

Key Clinical Pitfall

Secondary thrombocytosis poses little thrombotic risk regardless of platelet numbers in the absence of arterial disease or prolonged immobility 5. However, the critical distinction is identifying primary versus secondary causes—primary thrombocytosis has 2-3 times higher complication rates and requires hematology management 2. When in doubt about the etiology or if thrombocytosis persists despite treating secondary causes, refer to hematology rather than continuing observation 3.