Intro to anaemia and microcytic anaemia Flashcards
What is the definition of anaemia?
Reduced total red cell mass; use Hb concentration as a surrogate marker
Can also use haematocrti
What are the cut offs for anaemia?
Adult males; Hb <130 g/L, Hct 0.38-0.52
Adult females; Hb <120 g/L, Hct 0.37-0.47
How is Hb conc measured using a spectrophotometric method?
Lyse red cells to create Hb solution
Stabilise Hb molecules
Measure optical density at 540 nm
Hb conc calculated against known reference standard conc solution
What is beer’s law?
Optical density is proportional to the concentration of Hb
What is Hb/hct not a good marker of anaemia?
Rapid exsanguination
Haemodilution
What is the normal response to anaemia?
Increased red cell production - reticulocytosis
What are reticulocytes?
Red cells that have just left the bone marrow
Larger than average red cells
Still have RNA
Stain purple/ deeper red as a consequence
Blood film appears polychromatic
Why does polychromasia result in reticulocytes?
Residual RNa in the cell gives the classic blue-grey appearance
How is haematocrit calculated?
Red cell number x red cell size
What is the purpose of the blood film?
Cellular morphology
What does the reticulocyte count assess?
Marrow response
How can anaemia be classified on pathophysiological terms?
Decreased production (low retic count)
Increased loss or destruction of red cells (high retic count). Bleeding or haemolysis
Redistribution - (splenomegaly)
Decreased production (low retic count) :
Hypoproliferative - reduced amount of erythropoiesis
Maturation abnormality - erythropoiesis present but ineffective (cytoplasmic defects - impaired hemoglobinization. Nuclear defects - impaired cell division)
How can MCV determine the type of anaemia?
Low (microcytic) = issue with haemoglobinisation
High (macrocytic) = nuclear maturation
Where does haemoglobin synthesis occur in the cell?
Cytoplasm
Where is haem synthesized in the cell?
Mitochondrion
What makes up haem?
Porphyrin ring
Iron (Fe 2+)
What does iron deficiency anaemia present like?
Microcytic hypochromic anaemia: deficient haemoglobin synthesis (cytoplasmic defect)
What are the causes of hypochromic microcytic anaemia?
Haem deficiency: Iron deficiency Porphyrin synthesis (lead poisoning) Congenital sideroblastic anaemia Globin synthesis deficiency - thalassaemia (trait, intermedia, major)
What is the function of iron?
Oxygen transport (Hb, myoglobin) Electron transport (mitochondrial production of ATP)
In a normal patient (not on supplements), how much iron is absorbed per day?
1mg/ day
How much iron is stored in red cell Hb?
2500 mg
How is iron transported around the body?
Transferrin
How is iron stored in the liver and macrophages?
Ferritin
How much iron can bind to transferrin?
2 binding sites
What does the % saturation of transferrin measure?
Iron supply; low in iron deficiency anaemia and anaemia of chronic disease
Increased in genetic haemochromatosis
How much iron can a ferritin protein stor?
4000 ferric ions
What is serum ferritin an indirect measure of?
Storage iron
How can iron deficiency be confirmed?
Anaemia (decreased functional iron) and reduced storage iron (low serum ferritin)
What can cause a relative iron deficiency?
Women of child bearing age
Developing foetus
Pregnant women
What can cause an absolute iron deficiency?
Veggie/ vegan diets
Blood loss
Menorrhagia
Coeliac disease, achlorhydria
What can cause chronic blood loss?
Menorrhagia
GI; tumour, ulcer, NSAIDs
Haematuria
What is defined as heavy menstrual blood loss?
> 60ml i.e. >30mg iron/month
What are the sequential consequences of a negative iron balance?
Exhaustion of iron stores
Iron deficient erythropoiesis; falling red cell MCV
Microcytic anaemia
Epithelial changes; dry skin, koilonychia
Is iron deficiency anaemia a diagnosis?
No; a symptom. Need to determine why there is iron deficiency
