Essential thrombocytosis laboratory findings

Laboratory findings consistent with the diagnosis of essential thrombocytosis include abnormal complete blood count (elevated platelet count, leukocytosis, erythrocytosis), peripheral blood smear showing large platelets, megakaryocyte fragments and platelet aggregates, presence of JAK2 mutation, and absence of BCR-ABL or Philadelphia chromosome.^[1][2]

Essential thrombocytosis remains a diagnosis of exclusion, after ruling out reactive or secondary causes of thrombocytosis. Laboratory tests for the diagnosis of essential thrombocytosis include the following:^[1]

• Complete blood count (CBC)
  • Elevated platelet count
  • Leukocytosis and erythrocytosis may be present
  • Red cells are normocytic and normochromic, unless the patient had significant hemorrhage.
• Peripheral blood smear shows large platelets, megakaryocyte fragments and platelet aggregates.^[2]
• To rule out inflammatory disorders
  • Erythrocyte sedimentation rate (ESR) (normal in essential thrombocytosis)
  • C-reactive protein (CRP) (normal in essential thrombocytosis)
  • Fibrinogen (normal in essential thrombocytosis)
• To rule out iron deficiency and polycythemia vera
  • Serum ferritin (normal in essential thrombocytosis)
  • Hematocrit (normal in essential thrombocytosis)

• To rule out other myeloproliferative neoplasms
  • BCR-ABL or Philadelphia chromosome
• To check for genetic mutations
  • JAK2 mutation using PCR

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