Haematology 2

Question 1

How are reference ranges determined

Answer 1

Samples are collected from healthy volunteers with defined characteristics
They are analysed using the instrument and techniques used for patient samples
Data is analysed

Question 2

How can data with a normal distribution be analysed

Answer 2

Gaussian distribution
Determine the mean and standard deviation
95% range = mean +_ 2 SD

Question 3

What are caveats

Answer 3

Results within the 95% range determined from apparently health

Question 4

What is included in the full blood count

Answer 4

WBC - x10^9/l
RBS - x10^12/l
Hb -  g/l (haem conc)
Hct - l/l
PCV - % or l/l
MCV - fl
MCH - pg
MCHC - g/l
Platelet count - x10^9/l

Question 5

How are WBC, RBC and platelet count measured

Answer 5

Instruments that enumerate electronic impulses generated when cells flow between a light source and a sensor or when cells flow through an electrical field

Question 6

How is Hb measured

Answer 6

Convert haemoglobin to a stable form (cyanmethaemoglobin) and measuring light absorption at a specific wave length

Question 7

How is Haematocrit measured

Answer 7

Centrifuge a blood sample

Question 8

How is mean cell volume measured

Answer 8

Dividing total volume of red cells in a sample by number

Light scattering or by interruption of an electric field

MCV = PCVx1000/RBC

Question 9

How is mean cell haemoglobin measured

Answer 9

Amount of haemoglobin in a given volume of blood divided by no. of red cells in the same volume

Hb/TBC

Question 10

How is mean cell haemoglobin concentration measured

Answer 10

Amount of haemoglobin in a given volume of blood divided by the proportion of the sample represented by red cells

Measured electronically on the basis of light scattering

Hb/Hct

Question 11

What is the difference between the MCH and MCHC

Answer 11

MCH is the absolute amount of haemoglobin in an individual red cell
MCHC is the concentration of Haemoglobin in a red cell

Microcytic and microcytic anaemia - MCH tends to parallel MCV

Question 12

What are the pseudo causes of polycythaemia

Answer 12

Reduced plasma volume

Question 13

What are the true causes of polycythaemia

Answer 13

Blood doping or overtranfusion
Appropriately increased erythropoietin synthesis or use (tumour)
Independent of erythropoietin (intrinsic bone marrow disorder - polycythaemia vera)

Question 14

When is it normal for Hb. RBC and HCt to be lower/higher

Answer 14

higher in neonates

Children

Question 15

Describe polycythaemia vera

Answer 15

Erythropoietin-independent cause of polycythaemia
Classified as a myeloproliferative neoplasm
Leads to thick blood - hyper viscosity
Leads to vascular obstruction

Question 16

How is polycythaemia treated

Answer 16

No need for a high haemoglobin/hypervisocity is extreme - blood can be removed
Intrinsic bone marrow disease - drugs can be used to reduce bone marrow production of red cells