Haematology blood test basics

Question 1

Why is the reference range of haemoglobin (Hb g/L) lower in women?

Answer 1

Pre-menopausal women - menstruation + due to lack of testosterone production (testosterone stimulates RBC production)
Post-menopausal women - due to lack of testosterone production (testosterone stimulates RBC production)

Question 2

What happens to men’s Hb that have lost their testes in an accident or disease?

Answer 2

It falls.

Question 3

What is haematocrit?

Answer 3

The haematocrit index (Hct) expresses a proportion of whole blood that is taken up by all the blood cells. At a practical level this is equivalent to the proportion of red blood cells that make up whole blood as there are 1000x more RBC than WBC and 20x more RBC than plt.

Question 4

What blood parameters are provided directly from a sample of blood?

Answer 4

Hb, RBC, MCV

Question 5

How is the haematocrit (Hct) calculated?

Answer 5

RBC * MCV

Question 6

How is the mean cell haemoglobin calculated?

Answer 6

Hb / RBC

Question 7

How is the mean cell haemoglobin concentration calculated?

Answer 7

Hb / Hct

Question 8

What is the erythrocyte sedimentation rate?

Answer 8

The fall in the level of RBC in mm/hr when a thin column of blood is allowed to settle down under the influence of gravity for an hour.

Question 9

What differentials cause a raised ESR?

Answer 9

Cancer, infections, anaemia, inflammation, renal failure, rheumatoid arthritis, multiple myeloma and tuberculosis, myocardial infarction.

Question 10

What is the function of RBCs?

Answer 10

To carry oxygen.

Question 11

What are differentials for a hypoxic presentation?

Answer 11

1) Lung disease - COPD, Emphysema, Pneumonia
2) Heart disease - Valve disease, Cardiomyopathy, Heart Failure, Left ventricular aneurysm, Myocardial infarction
3) Atherosclerosis
4) Oedema, Cellulitis
5) Anaemia

Question 12

What are the red blood cell indices?

Answer 12

MCV, MCH, MCHC

Question 13

What are the signs and sx of anaemia?

Answer 13

Signs: Pallor, Tachycardia, Glossitis, Koilonychia, Dark urine
Sx: Decreased work/productivity, fatigue, lethargy, weakness, dizziness, palpitations, SOB, rarely: headaches, tinnitus

Question 14

What are the causes of anaemia?

Answer 14

1) Depressed red blood cell production from the bone marrow
2) Diet deficiency and organ disease
3) Loss of mature red blood cells
4) Haemoglobinopathy

Question 15

How does red blood cell size correspond to different types of anaemia?

Answer 15

Microcytic cells: iron-deficient anaemia, sickle cell disease, thalassaemia
Normocytic: leukaemia, acute or chronic blood loss
Macrocytic: B12 deficiency, pernicious anaemia, liver disease, pregnancy

Question 16

What are causes of increased red cell indices?

Answer 16

Polycythaemia 
Reactive erythrocytosis (to hypoxia)

Question 17

What are the 5 white blood cell types recognised in normal blood?

Answer 17

Neutrophils (40-75%), lymphocytes (20-45%), monocytes (2-10%), eosinophils (1-6%) and basophils (<1%). Blasts/atypical cells may also be present - hardly any.

Question 18

What name may neutrophils also be called?

Answer 18

Phagocytes

Question 19

Where are lymphocytes mainly present?

Answer 19

In the lymphoid tissue: lymph nodes, bone marrow, liver and spleen.

Question 20

What are monocyte’s action and what are they known as in tissues?

Answer 20

Phagocytosis. In tissues they are called macrophages.

Question 21

What are eosinophil’s action?

Answer 21

Defence against parasites. Also active in allergy, hay fever, asthma and skin disease.

Question 22

When may basophil numbers be high?

Answer 22

Acute hypersensitivity, atopy, leukaemias (specify when slides are released)

Question 23

What ethnicity may have naturally low levels of white cell numbers?

Answer 23

African descent.

Question 24

What are the signs and sx of a potential transfusion incompatibility?

Answer 24

Signs: Fever >40 dc, hypotension, oozing from wounds, haemoglobinuria, tachycardia (>100bpm)
Sx: Cough +/or headache, flushing, rash, anxiety, agitation, chills, nausea, vomiting, trembles/shakes, SOB, chest pain