Introduction to anaemia

Question 1

Anaemia is the name for reduced total red blood cell mass. What can be used as a marker for anaemia?

Answer 1

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

Question 2

How is haemoglobin concentration measured?

Answer 2

RBCs are lysed to create Hb solution, Hb molecules are stabilised, optical density at 540nm is measured, Hb concentration is calculated against known reference

Question 3

How is haematocrit measured?

Answer 3

Ratio of the whole blood that is RBCs if the sample was left to settle

Question 4

What are reticulocytes?

Answer 4

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.

Question 5

What happens to reticulocytes as a result of anaemia?

Answer 5

Reticulocytosis - increase in reticulocytes - this takes a few days

Question 6

What investigations are carried out for anaemia?

Answer 6

Hb conc., number of RBCs, MCV, haematocrit, mean cell Hb, mean cell Hb conc., FBC, blood film, reticulocyte count

Question 7

How is anaemia pathophysiologically classified?

Answer 7

Either decreased production (low reticulocyte count) or increased loss/destruction of RBCs (high reticulocyte count)

Question 8

What are the 2 possible mechanisms for anaemia due to decreased production?

Answer 8

Hypoproliferative - reduced amount of erytropoiesis or maturation abnormality - erythropoiesis is present but ineffective e.g. nuclear or cytoplasmic defects

Question 9

What are the 2 possible mechanisms for anaemia due to increased loss/destruction of RBCs?

Answer 9

Bleeding or haemolysis

Question 10

Mean cell volume (MCV) is a useful tool in distinguishing cytoplasmic and nuclear defects. What is indicated if MCV is low and high respectively?

Answer 10

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

Question 11

Describe microcytic anaemias in terms of cells and Hb content

Answer 11

Shortage in haem and globins results in small RBCs with a low Hb content - cells are microcytic and hypochromic (lacking in colour)

Question 12

What is the cause of hypochromic, microcytic anaemias?

Answer 12

Deficient haemoglobin synthesis - cytoplasmic defect

Question 13

Name some examples of causes of hypochromic microcytic anaemia

Answer 13

Haem deficiency - lack of iron for erythropoiesis e.g. iron deficiency., problems with porphyrin synthesis e.g. lead poisoning (very rare)
Globin deficiency - thalassaemia

Question 14

Where is most of the iron in the body found?

Answer 14

In bone marrow - tiny amount in circulation moving to/from storage site

Question 15

What is circulating iron bound to?

Answer 15

Transferrin

Question 16

Where is iron transferred?

Answer 16

To the bone marrow macrophages that feed it to red cell precursors

Question 17

Where is iron stored?

Answer 17

Ferritin in the liver

Question 18

Name some investigations used to assess iron status

Answer 18

Hb - functional iron
Serum iron, transferrin, transferrin saturation - transported iron
Serum ferritin - storage iron

Question 19

What is transferrin?

Answer 19

Protein with 2 binding sites for iron atoms

Question 20

What does transferrin do?

Answer 20

Transports iron from donor tissues e.g. macrophages, hepatocytes to tissues expressing transferrin receptors (esp. erythroid marrow)

Question 21

% saturation of transferrin with iron measures what? Name some examples of when this is increased and reduced

Answer 21

Measures iron supply
Reduced in iron deficiency and anaemia of chronic disease
Increased in haemochromatosis

Question 22

What is ferritin?

Answer 22

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

Question 23

What are some causes of iron deficiency?

Answer 23

Relative deficiency - esp.women of child bearing age and children
Absolute deficiency - vegetarian diets
Blood loss - usually GI bleeds
Malabsorption - coeliac disease, achlorhydria

Question 24

What are some causes of chronic blood loss leading to iron deficiency?

Answer 24

Menorrhagia, GI tumours, ulcers, NSAIDs, haematuria

Question 25

What happens as a result of negative iron balance?

Answer 25

Exhaustion of iron stores, iron deficient erythropoiesis (falling MCV), microcytic anaemia, epithelial changes (skin, koilonychia)