CBC
Chem 7
ESR
Bone marrow biopsy sometimes needed
Per the WHO guidelines, diagnosis of<unk>  requires all of the following:
Essential thrombocytosis
Myelofibrosis
Polycythemia vera
Chronic myelogenous leukemia 
Immune thrombocytopenic purpura
Polycythemia vera 
Thrombotic thrombocytopenic purpura
Acute blood loss