Full Blood Count
 

Mean Cell Volume

 
 
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Overview

  • The mean cell volume (MCV) is a measure of the average volume of a red blood cell.
  • Assessment of red blood cell size - the presence of normocytosis, microcytosis or macrocytosis - is the first step in the assessment of patients with anaemia as it can rapidly be used to narrow down the likely causes.
      • Normal Range

      • 80-100 fL
    • Interpretation

    • Microcytosis: abnormally small red blood cellsIron deficiency, anaemia of chronic disease, thalassaemia, lead poisoning
    • Normocytosis: normally sized red blood cellsAplastic anaemia, acute haemorrhage, haemolysis
    • Macrocytosis: abnormally large red blood cellsB12/folate deficiency, alcoholism, myelodysplastic syndrome

Microcytosis

  • Microcytosis refers to the presence of small red cells with mean corpuscular volume <80 fL.
    • Causes of Reduced Mean Cell Volume

    • Iron deficiency anaemia - nutritional deficiency, blood loss, malabsorption, pregnancy
    • Anaemia of chronic disease (chronic infection / inflammation / malignancy)
    • Thalassaemia
    • Congenital sideroblastic anaemia
    • Lead poisoning
    • Hyperthyroidism

Macrocytosis

  • Macrocytosis refers to the presence of large red blood cells with mean corpuscular volume >100 fL.
  • Macrocytic cells may occur in the context of megaloblastic anaemia, which is typically associated with macroovalocytes (large oval-shaped cells) and hypersegmented neutrophils; they may be seen due to an overabundance of reticulocytes (immature non-nucleated red cells); or may be due to other causes such as liver disease, hypothyroidism or myelodysplastic syndrome.
    • Causes of Macrocytosis

    • Megaloblastic

    • B12 deficiency
    • Folate deficiency
    • Scurvy
    • Drugs - methotrexate, chemotherapy, reverse transcriptase inhibitors, valproate, phenytoin, nitrous oxide, trimethoprim
    • Reticulocytosis

    • Haemolytic anaemia
    • Haemorrhage
    • Recovery following bone marrow suppression
    • Other

    • Chronic liver disease
    • Chronic alcohol abuse
    • Myelodysplastic syndrome
    • Post splenectomy
    • Aplastic anaemia
    • Hypothyroidism
 
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