Introduction to haematology

Question 1

What is haematopoiesis?

Answer 1

• The physiological developmental process that gives rise to the cellular components of blood
• A single multipotent haemopoietic stem cell can divide and differentiate to form different cell lineages that will populate the blood

Question 2

What is a haemopoietic stem cell?

Answer 2

• Differentiation potential for all lineages
• High proliferative potential
• Long term activity throughout the lifespan of the individual
• Self renewal

Question 3

What is symmetric self-renewal?

Answer 3

Increase stem cell pool – NO generation of differentiated progeny

Question 4

What is asymmetric self-renewal?

Answer 4

Maintain stem cell pool – generation of differentiate progeny.

Question 5

What is lack of self-renewal?

Answer 5

Deplete stem cell pool – generation of ONLY differentiated progeny

OR

Maintain stem cell pool – NO differentiated progeny

Question 6

What are the two haemopoietic lineages?

Answer 6

• Myeloid

- Lymphoid

Question 7

At what point in human development does heamopoiesis start?

Answer 7

Day 27

Question 8

Where does heamopoiesis start?

Answer 8

In the aorta-gonado-mesonephros region,

expands rapidly at day 35, then disappear at day 40.

Question 9

Why does the aorta-gonado-mesonephros region disappear?

Answer 9

This disappearance correlates with the migration of these hematopoietic stem cells to the foetal liver, which becomes the subsequent site of haemopoiesis.

Question 10

What are the features of erythrocytes?

Answer 10

Bi-concave discs, 7.5 µM diameter

Question 11

What is the lifespan of an erythrocyte?

Answer 11

120 days

Question 12

What is anaemia?

Answer 12

Reduced erythrocytes

Question 13

What is polycythaemia?

Answer 13

Abnormally raised erythrocytes

Question 14

What is relative polycythaemia?

Answer 14

Plasma volume is reduced so erythrocytes appear raised

Question 15

What are granulocytes?

Answer 15

Have cytoplasmic granules (neutrophils, eosinophils, basophils)

Question 16

What is the function of neutrophils?

Answer 16

Phagocytes

Question 17

What is neutrophilia?

Answer 17

Increased numbers of neutrophils

Question 18

Why might neutrophil levels be increased?

Answer 18

Bacterial infection and inflammation

Question 19

What is the lifespan of neutrophils?

Answer 19

A few hours

Question 20

What is neutropenia?

Answer 20

Decreased numbers of neutrophils

Question 21

Why would eosinophil levels be increased?

Answer 21

• Parasitic infection

- Allergies

Question 22

Why might basophil levels be increased?

Answer 22

CML

Question 23

What are monocytes?

Answer 23

• Phagocytic & antigen-presenting cells
• Migrate to tissues & are then identified as “macrophages” or “histiocytes”
  e. g. Kupffer cells in liver
  e. g. Langerhans cells in skin

Question 24

What is monocytosis and why might it occur?

Answer 24

Increased numbers of monocytes. Can happen in TB.

Question 25

What is the function of NK cells?

Answer 25

- Recognise “non-self” e. g. Cells, viruses - Large granular lymphocytes

Question 26

What are B-lymphocytes?

Answer 26

- Adaptive immune system - rearrange the immunoglobulin genes to enable antigen specific antibody production - humoral immunity

Question 27

What are T-lymphocytes?

Answer 27

- Adaptive immune system - rearrange the T-cell antigen receptor - cell-mediated immunity - target specific cytotoxicity - Interact with B cells, macrophages - Regulate immune responses

Question 28

What is lymphocytosis and why might it occur?

Answer 28

Increased numbers of lymphocytes. e. g. atypical lymphocytes of glandular fever (infectious mononucleosis) e. g. Chronic lymphocytic leukaemia

Question 29

What is lymphopenia and why might it occur?

Answer 29

Decreased numbers of lymphocytes. e.g. post bone marrow transplant

Question 30

What is plasmocytosis and why might it occur?

Answer 30

Increased numbers of plasma cells e.g. infection, myeloma

Question 31

What are platelets derived from?

Answer 31

Bone marrow megakaryocytes

Question 32

What measures are included in a full blood count?

Answer 32

- Haemoglobin concentration - Red cell parameters - MCV (mean cell volume) - MCH (mean cell Hb) - White Cell Count (WCC) - Platelet Count

Question 33

What measures are included in a coagulation test?

Answer 33

- Prothrombin Time - Activated Partial Thromboplastin Time - Thrombin Time

Question 34

How is a bone marrow aspirate & trephine performed?

Answer 34

Under local anaesthetic, liquid marrow is aspirated from the posterior iliac crest of the pelvis and a trephine core biopsy is then taken with a hollow needle.

Question 35

How is a reference range established?

Answer 35

- Define the reference population - Reference population should be relevant to the test population - Consider if separate ranges are required for adults versus children, men versus women, and so forth. - Determine the expected range of interindividual variation

Question 36

What is a reference range?

Answer 36

The set of values for a given test that incorporates 95% of the normal population

Question 37

What percentage of results fall within the reference range?

Answer 37

95%

Question 38

What is sensitivity?

Answer 38

- The proportion of abnormal results correctly classified by the test. - Expresses the ability to detect a true abnormality

Question 39

What is specificity?

Answer 39

- The proportion of normal results correctly classified by the test - Expresses the ability to exclude an abnormal result in a healthy person

Question 40

In what situation might an abnormal lymphocyte count be expected?

Answer 40

- Post-splenectomy, mild lymphocytosis | - 3 months post-bone marrow transplant lymphopenia

Question 41

What is microcytic anaemia?

Answer 41

MCV

Question 42

What are the causes of microcytic anaemia?

Answer 42

- Iron deficiency - Thalassaemia - Anaemia of chronic disease (some) - Lead poisonng - Sideroblastic anaemia (some cases)

Question 43

What is normocytic anaemia?

Answer 43

MCV 80-95 fl & MCH ≥ 27 pg

Question 44

What are the causes of normocytic anaemia?

Answer 44

- Many haemolytic anaemias - Anaemia of chronic disease (some cases) - After acute blood loss - Renal disease - Mixed deficiencies - Bone marrow failure (e.g. post-chemotherapy, infitration by carcinoma etc)

Question 45

What is macrocytic anaemia?

Answer 45

MCV >95 fl

Question 46

What are the causes of macrocytic anaemia?

Answer 46

Megaloblastic: Vitamin B12 or folate deficiency | Non-megaloblastic: alcohol, liver disease, myelodysplasia, aplastic anaemia etc