Peripheral smear – Platelets

PERIPHERAL SMEAR – PLATELETS
  • What is the normal count of platelets
    • 1,50,000 to 4,00,000 /µL of blood

 

  • What is the size of platelet
    • Platelets are approximately 2µm – 4 µm in diamtre

 

  • How do you assess adequacy of platelets by blood smear study
    • Average  number of platelet  count per  oil immersion(100x) field multiplied by  20,000/mm3 gives appropximate platelet count

 

  • What is thrombocytopenia
    • Decrease in platelet count below 150000/µL is called thrombocytopenia

 

  • What are the causes of thrombocytopenia
    • Acute leukemia
    • Aplastic anemia
    • Idiopathic thrombocytopenic purpura
    • Drugs – Thiazides, Chloramphenicol and anticancer drugs
    • Megaloblastic anemia
    • Myelodysplastic syndrome
    • Hypersplenism (sequestration)
    • Massive blood transfusion
    • infectious – Infectious mononucleosis, HIV, Cytomegalo virus
    • Disseminated intravascular coagulation
    • Thrombotic thrombocytopenic purpura
    • Microangiopathic hemolytic anemia

 

  • What is thrombocytosis
    • Increased platelet count above 4,00,000/µL

 

  • What are the causes of thrombocytosis
    • Physiologic causes – Parturition, Excercise, EPinephrine
    • Pathologic causes
      • Primary causes
        • Myeloproliferative syndrome
        • Polycythemia Vera
        • CML
        • Essential thrombocythemia
        • Myelofibrosis
      • Secondary causes
        • Neoplasia
        • Infectious and inflammatory conditions
        • Asplenia
        • Iron deficiency anemia
        • Post surgery

 

  • What is the relationship between Platelet count and severity of bleeding
    • Platelet count >50,000/µL – No spontaneous bleeding
    • Platelet count 10,000/µL – 50000/µL – Spontaneous bleeding in skin, mucous  membrane and post traumatic
    • Platelet count less than 10000/µL –  serious GI bleeding and  genitourinary bleeding

 

  • What is the blood and bone marrow picture in ITP
    • Blood picture
      • Thrombocytopenia (usually less than 80000/µL)
      • Giant plateltes may be seen
      • Anemia if associated with blood loss
      • WBC count may be normla
    • Bone marrow picture
      • Hypercellular marrow with hyperplasia of megakarycytes
      • Megakarycytes may be mature or immature
      • Small immature megakarycytes with unlobulated single nuclei and scanty basophilic cytoplasm predominates
      • Erythroid hyperplasia in response to anemia
      • Myelopoiesis is normal
      • Iron stores are depleted if there is severe blood loss

 

  • Enumerate the qualitative disorders of platelet function
    • Hereditary disorders
      • Glanzmann thrombasthenia – defects in platelet aggregation
      • Bernard- Soulier syndrome – defects in platelet adhesion
      • Grey platelet syndrome – Defect in release of secretions from granules
      • Dense body deficiency
        • Alpha-delta granules deficiency
        • Delta granule deficiency
      • Abnormal receptor mediated signal transduction and secretion –
        • Cyclo-oxygenase deficiency
        • Thromboxane synthetase deficiency
        • Impaired response to thromboxane A2
    • Acquired disorders of platelet function
      • Uraemia
      • Drug induced platelet dysfunction
      • Paraproteinemia
      • Myelodysplastic syndromes
References
  • Dr.Tejindar Singh, Dr.K Uma Chaturvedi. Practical pathology, Third edition, 2015.
  • P. Chakraborthy, GargiChakraborthy. Practical Pathology, 2002.
  • Dr.Ganga S.Pilli. Practical Pathology, 2007
  • Sabitri Sanyal, Aparna Bhattacharya. Clinical Pathology. A Practical Manual. Third edition, 2017
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