From the Research
The workup for an elevated isolated platelet count (thrombocytosis) should begin with a thorough history, physical examination, and basic laboratory tests to distinguish between primary and secondary causes, as outlined in the most recent study 1. The initial evaluation should include a complete blood count with peripheral smear, comprehensive metabolic panel, inflammatory markers (ESR, CRP), iron studies, and JAK2 V617F mutation testing. Key factors to consider in the history and physical examination include:
- Smoking
- Thrombosis
- Splenectomy
- Active malignancy
- Chronic inflammatory disease
- Iron deficiency anemia These factors can help differentiate between primary and secondary thrombocytosis, with certain factors such as active malignancy, chronic inflammatory disease, splenectomy, and iron deficiency being more commonly associated with secondary thrombocytosis 1. If primary thrombocytosis is suspected, bone marrow aspiration and biopsy with cytogenetic studies should be performed to evaluate for myeloproliferative neoplasms such as essential thrombocythemia. Additional molecular testing for CALR and MPL mutations may be indicated if JAK2 is negative. For secondary thrombocytosis, addressing the underlying cause such as iron deficiency, infection, inflammation, or malignancy is crucial. Risk stratification is important for primary thrombocytosis, with high-risk patients (age >60, prior thrombosis, platelet count >1,500,000/μL) typically requiring cytoreductive therapy with hydroxyurea (starting at 500-1000 mg daily) or anagrelide (0.5 mg twice daily, titrated upward). Low-dose aspirin (81-100 mg daily) is often recommended for all patients with primary thrombocytosis unless contraindicated, as outlined in the approach to investigating patients with persistent thrombocytosis 1. This approach helps prevent thrombotic complications while the diagnostic evaluation proceeds, as platelets in myeloproliferative disorders are often functionally abnormal and can lead to both bleeding and clotting events. The study by 1 provides the most recent and highest quality evidence for the workup of elevated isolated platelet count, and its findings should be prioritized in clinical practice.