Diagnosis of Essential Thrombocythemia Complete blood count (CBC) and peripheral blood smear Exclusion of causes of secondary thrombocytosis and other myeloproliferative neoplasms Cytogenetic studies JAK2 mutation and, if negative, CALR or MPL mutation analysis Rarely, bone marrow aspirate and biopsy The platelet count is > 450, 000 / mcL (> 450 × 10 9 / L), but can be > 1, 000, 000 / mcL (> 1000 × 10 9 / L).