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Haematology > Anaemia and Microcytic Anaemias > Flashcards

Anaemia and Microcytic Anaemias Flashcards

1
Q

What is anaemia?

A

Reduced total red cell mass

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2
Q

Is it easy to measure total red cell mass?

A

NO - so this is not routinely done

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3
Q

As total red cell mass is difficult to measure, what can be done measured instead?

A
  • Haemoglobin

* Haematocrit

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4
Q

Outline the Hb and haematocrit levels to diagnose anaemia in adult males.

A
  • Hb <130g/L

* Hct 0.38-0.52

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5
Q

Outline the Hb and haematocrit levels to diagnose anaemia in adult females.

A
  • Hb <120g/L

* Hct 0.37-0.47

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6
Q

Where does red blood cell production take place?

A

Bone marrow

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7
Q

What type of method is used to measure haemoglobin concentration?

A

Spectrophotometric method

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8
Q

Outline the steps in the method of measuring haemoglobin concentration.

A
  • Burst (lyse) the red cells to create Hb solution
  • Stabilise the Hb molecules (cyan-metHb)‏
  • Measure the optical density (OD) at 540nm
  • OD Proportional to the concentration (Beer’s Law)
  • Hb concentration calculated against known reference standard cyan-metHb concentration solution
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9
Q

How is haematocrit measured?

A

The ratio (also commonly expressed as the percentage) of the whole blood that is red cells if the sample was left to settle

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10
Q

In rare situations, haemoglobin/haematocrit are not good indicators of anaemia e.g a rapid bleed and haemodilution

A

T

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11
Q

In what situations are Hb/haematocrit not good indicators of anaemia?

A
  • Rapid bleed

* Haemodilution

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12
Q

Describe why measuring Hb/haematocrit in a rapid bleed is not a good indicator of anaemia.

A

If 50% of blood volume is lost, the patient will obviously be anaemic as their red cell mass will have dropped by 50%

However, as both blood volume and red cell mass are decreased in proportion to eachother, the concentration of Hb will initially remain the same

True red cell mass is only apparent after a few days once fluid shifts have occurred

If you take measurements too early, you will not see a decrease of Hb

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13
Q

Describe why measuring Hb/haematocrit in haemodilution is not a good indicator of anaemia.

A

For example, later in pregnancy, plasma volume increases, making Hb concentration lower despite red cell mass being the same

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14
Q

What is increased red cell production known as?

A

Reticulocytosis

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15
Q

What is a reticulocyte?

A

A reticulocyte is a young red blood cell, just after it has left the bone marrow

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16
Q

Describe the appearance of a reticulocyte.

A
  • Larger than the average cell
  • Contains RNA
  • Stains deep purple/red
  • Polychromatic
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17
Q

Up regulation of reticulocyte production by the bone marrow in response to anaemia takes a few days

A

T

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18
Q

What can automated analysis of RBC’s tell us about RBC’s?

A
  • Cell size
  • Cell count
  • Light-scattering properties
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19
Q

Outline the 3 measured indices of a red cell.

A
  • The haemoglobin concentration
  • The number of red cell (concentration)
  • The size of the red cells (mean cell volume or MCV)
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20
Q

Outline the 3 calculated indices of a red cell.

A
  • Haematocrit
  • Mean cell haemoglobin
  • Mean cell haemoglobin concentration
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21
Q

What does reticulocyte count assess?

A

Bone marrow response

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22
Q

By which 2 methods is anaemia classified?

A
  • Pathophysiology

* Morphological characteristics

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23
Q

In terms of pathophysiology, anaemia can be classified as either __________ ____ or __________ __________

A
  1. Increased loss

2. Decreased production

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24
Q

What 2 things can decreased production be due to?

A
  • Hypo-proliferation – reduced amount of erythropoiesis

* Maturation abnormality – erythropoiesis is present but ineffective

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25
Q

What are the 2 most common causes of a maturation abnormality, which causes decreased production of red cells?

A
  • Cytoplasmic defects – impaired haemoglobinisation

* Nuclear defects – impaired cell division

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26
Q

Microcytic anaemia has a ____ MCV

A

LOW

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27
Q

Macrocytic anaemia has a ____ MCV

A

HIGH

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28
Q

LOW RETICULOCYTE COUNT is seen when?

A

In a decreased production of red cells

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29
Q

HIGH RETICULOCYTE COUNT is seen when?

A

In increased loss or destruction of red cells

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30
Q

Where is haemoglobin synthesised?

A

Cytoplasm

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31
Q

What 2 things are needed to make haemoglobin?

A
  • Globins

* Haem – porphyrin ring + Iron (Fe2+)

32
Q

What does a shortage of globins or haem do?

A

Shortage of these components results in small red cells with low haemoglobin count

33
Q

Describe the cells seen in microcytic anaemia.

A

The cells are microcytic (small)‏ and hypochromic (lacking in colour)‏

34
Q

What is colour of RBC’s measured by?

A

MCH (mean cell haemoglobin)

35
Q

What are the 2 main groups of causes of Hypochromic, Microcytic Anaemias?

A
  • Haem deficiency

* Globin deficiency

36
Q

Iron deficiency is the commonest cause of microcytic anaemia worldwide

37
Q

What is the most common cause of a globin deficiency?

A

Thalassaemia (trait, intermedia, major) – globin chain defect

38
Q

List 3 causes of a haem deficiency.

A
  • Lack of iron for erythropoiesis
  • Problems with porphyrin synthesis e.g lead poisoning - ‘Pyridoxine responsive anaemias’
  • Congenital Sideroblastic Anaemia (very rare)
39
Q

What 2 things is iron essential for?

A
  • Oxygen transport – haemoglobin and myoglobin

* Electron transport – mitochondrial production of ATP

40
Q

Iron is potentially toxic and needs to be handled safely by the body – generates free radicals

41
Q

Describe the structure of adult haemoglobin.

A

4 globin (protein) sub-units, each containing a single haem group

42
Q

Each haem group has a Fe2+ ion and porphyrin ring

43
Q

1 haem group binds to one O2 molecule

44
Q

How much iron to we absorb per day?

A

1mg/day of iron

45
Q

How can the amount of iron in the blood be roughly calculated?

A

The amount of iron in the blood can be roughly calculated by halving the volume of blood

46
Q

Iron is stored in the liver as a molecule known as ferritin

47
Q

How is iron stored?

A

Iron is stored in the liver as a molecule known as ferritin

48
Q

Most of the iron in the body is in haemoglobin

49
Q

Where is most of the iron in the body?

A

Most of the iron in the body is in haemoglobin

50
Q

We are only able to absorb small amounts of iron !!

51
Q

Circulating iron is bound to transferrin

52
Q

What is circulating iron bound to?

A

Transferrin

53
Q

Iron is transferred to the bone marrow macrophages that ‘feed it’ to red cell precursors

54
Q

List all the ways we can assess iron status.

A

Functional Iron

  • Haemoglobin

Transported Iron

  • Serum iron
  • Transferrin
  • Transferrin saturation

Storage Iron

  • Serum ferritin
55
Q

Describe the structure of transferrin.

A

A protein with two binding sites for iron atoms

56
Q

When might transferrin levels be reduced?

A
  • Reduced in anaemia of chronic disease
57
Q

When might transferrin levels be increased?

A
  • Increased in genetic haemachromatosis
58
Q

What does transferrin tell us about?

A

Tells us about the availability of iron, rather than the amount of iron in the system

59
Q

What is the normal range of transferrin?

60
Q

What is ferritin?

A

A large intracellular protein

Spherical protein stores up to 4000 ferric ions

61
Q

What does ferritin reflect?

A

Reflects intracellular ferritin synthesis in response to iron status of the host

62
Q

Serum ferritin is an easily measured indirect measure of storage iron

63
Q

Low ferritin means iron deficiency

64
Q

Ferritin is one of the acute phase proteins. What does this mean?

A

It can therefore be high in acute illness, but patient may actually be iron deficient

65
Q

Iron deficiency can be confirmed by a combination of anaemia (decreased functional iron) and reduced storage iron (low serum ferritin)

66
Q

List 3 causes of chronic blood loss.

A
  • Menorrhagia
  • Gastrointestinal – tumours, ulcers, NSAID’s
  • Haematuria
67
Q

____________ is the most common cause of chronic blood loss worldwide

A

Menorrhagia

68
Q

Outline 4 consequences of negative iron balance.

A
  1. Exhaustion of iron stores
  2. Iron deficient erythropoiesis - falling red cell MCV
  3. Microcytic anaemia
  4. Epithelial changes - skin, koilonychia
69
Q

What are the 3 main causes of iron deficiency.

A
  • Reduced diet consumption
  • Losing iron
  • Reduced absorption of iron
70
Q

What 3 things can reduce the absorption of iron?

A
  • Malabsorption (relatively uncommon)
  • Coeliac disease
  • Achlorhydria‏ (no acid in stomach)
71
Q

How can someone lose iron?

A

Blood loss (usually gastrointestinal)

72
Q

Outline the 2 types of reduced diet intake of iron.

A
  • Relative Deficiency – especially women of child bearing age and children
  • Absolute Deficiency – vegetarian and vegan diets
73
Q

If you have heavy periods/blood loss, what can you lose the ability to do?

A

Absorb iron

74
Q

What is heavy menstrual blood loss defined as?

A

> 60ml – so >30mg iron/month

75
Q

What is average menstrual blood loss?

A
  • Average 30-40ml/month

* Equivalent to 15-20mg/month

76
Q

Describe occult blood loss.

A

A small volume gastrointestinal blood loss can occur without any symptoms or signs of bleeding

It can outstrip the maximum dietary iron absorption of iron, and result in anaemia

77
Q

How can you treat iron deficiency?

A

Iron absorption can be increased by iron supplements

Haematology (26 decks)

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