Introduction to anaemia Flashcards
Anaemia is the name for reduced total red blood cell mass. What can be used as a marker for anaemia?
Haemoglobin concentration and haematocrit.
Hb <130g/L and Hct 0.38-0.52 in males = anaemia
Hb<120g/L and Hct 0.37-0.47 in females = anaemia
How is haemoglobin concentration measured?
RBCs are lysed to create Hb solution, Hb molecules are stabilised, optical density at 540nm is measured, Hb concentration is calculated against known reference
How is haematocrit measured?
Ratio of the whole blood that is RBCs if the sample was left to settle
What are reticulocytes?
They are RBCs that have just left the marrow. They’re larger than average RBCs and stain deeper red as a result. Blood film appears polychromatic.
What happens to reticulocytes as a result of anaemia?
Reticulocytosis - increase in reticulocytes - this takes a few days
What investigations are carried out for anaemia?
Hb conc., number of RBCs, MCV, haematocrit, mean cell Hb, mean cell Hb conc., FBC, blood film, reticulocyte count
How is anaemia pathophysiologically classified?
Either decreased production (low reticulocyte count) or increased loss/destruction of RBCs (high reticulocyte count)
What are the 2 possible mechanisms for anaemia due to decreased production?
Hypoproliferative - reduced amount of erytropoiesis or maturation abnormality - erythropoiesis is present but ineffective e.g. nuclear or cytoplasmic defects
What are the 2 possible mechanisms for anaemia due to increased loss/destruction of RBCs?
Bleeding or haemolysis
Mean cell volume (MCV) is a useful tool in distinguishing cytoplasmic and nuclear defects. What is indicated if MCV is low and high respectively?
MCV low (microcytic) - consider problems with haemoglobinisation (haemoglobin synthesis occurs in the cytoplasm - defects result in small cells) MCV high (macrocytic) - consider problems with maturation
Describe microcytic anaemias in terms of cells and Hb content
Shortage in haem and globins results in small RBCs with a low Hb content - cells are microcytic and hypochromic (lacking in colour)
What is the cause of hypochromic, microcytic anaemias?
Deficient haemoglobin synthesis - cytoplasmic defect
Name some examples of causes of hypochromic microcytic anaemia
Haem deficiency - lack of iron for erythropoiesis e.g. iron deficiency., problems with porphyrin synthesis e.g. lead poisoning (very rare)
Globin deficiency - thalassaemia
Where is most of the iron in the body found?
In bone marrow - tiny amount in circulation moving to/from storage site
What is circulating iron bound to?
Transferrin
Where is iron transferred?
To the bone marrow macrophages that feed it to red cell precursors
Where is iron stored?
Ferritin in the liver
Name some investigations used to assess iron status
Hb - functional iron
Serum iron, transferrin, transferrin saturation - transported iron
Serum ferritin - storage iron
What is transferrin?
Protein with 2 binding sites for iron atoms
What does transferrin do?
Transports iron from donor tissues e.g. macrophages, hepatocytes to tissues expressing transferrin receptors (esp. erythroid marrow)
% saturation of transferrin with iron measures what? Name some examples of when this is increased and reduced
Measures iron supply
Reduced in iron deficiency and anaemia of chronic disease
Increased in haemochromatosis
What is ferritin?
Large intracellular protein, tiny amount of ferritin present in serum (reflects intracellular ferritin synthesis in repsonse to iron status of the host), serum ferritin is an easily measured indirect measure of storage iron. Low ferritin means iron deficiency
What are some causes of iron deficiency?
Relative deficiency - esp.women of child bearing age and children
Absolute deficiency - vegetarian diets
Blood loss - usually GI bleeds
Malabsorption - coeliac disease, achlorhydria
What are some causes of chronic blood loss leading to iron deficiency?
Menorrhagia, GI tumours, ulcers, NSAIDs, haematuria
What happens as a result of negative iron balance?
Exhaustion of iron stores, iron deficient erythropoiesis (falling MCV), microcytic anaemia, epithelial changes (skin, koilonychia)
