Physiological basis
Platelets are released from megakaryocytes in bone marrow and are important for normal hemostasis. An estimated platelet count may be obtained from blood smear by multiplying the number of platelets per 100 × oil immersion field by 10,000.
Increased in: |
Decreased in: |
Myeloproliferative disorders (polycythemia vera, chronic myeloid leukemia, essential thrombocythemia, myelofibrosis), some myelodysplastic disorders, acute blood loss, postsplenectomy, pre-eclampsia, reactive thrombocytosis secondary to inflammatory disorders, infection, tissue injury, iron deficiency, malignancies. |
Bone marrow suppression or replacement/infiltration, myelodysplasia, chemotherapy, drugs, alcohol, infection (eg, HIV), congenital marrow failure (eg, Fanconi anemia), Increased destruction or excessive pooling: hypersplenism, DIC, TTP, platelet antibodies (ITP), drugs (eg, quinidine, cephalosporins, clopidogrel) |
Comments
Platelet counts are determined in patients with suspected bleeding disorders, purpura or petechiae, leukemia/lymphoma, or DIC, and in patients on chemotherapy, and to determine the response to platelet transfusions. There is little tendency to bleed until the platelet count falls below 0.2Lakhs/cumm. Bleeding due to low platelet counts typically presents as petechiae, epistaxis, and gingival bleeding. For invasive procedures, platelet counts > 0.5 Lakhs/cumm are desirable.