Deciding what is normal and interpreting blood counts

Question 1

State some factors that affect what is ‘normal’.

Answer 1

Age 
Gender 
Ethnic origin  
Physiological status  
Altitude 
Nutritional status  
Cigarette smoking  
Alcohol intake

Question 2

What is the difference between a reference range and a normal range?

Answer 2

Reference Range = derived from a carefully defined reference population e.g. children 5-10 years
Normal Range = much vaguer – it should represent the people that live in the local area and come to the hospital

Question 3

How is a reference range determined?

Answer 3

Samples are collected from healthy volunteers with defined characteristics.
The data is analysed by appropriate techniques.
If the data follows a normal (Gausian) distribution, you can determine what is normal by taking the mean and taking 2 standard deviations on either side. Between the 2 SDs on either side, you will have 95% of the data.

Question 4

What unit is MCV measured in?

Answer 4

Femtolitres, fL (10^-15L)

Question 5

What unit is MCH measured in?

Answer 5

Picograms, pg (10^-12g)

Question 6

How are these parameters measured now?

Answer 6

It is determined indirectly by light scattering or by interruption of an electrical field

Question 7

units of WBC

Answer 7

white blood cell count in a given volume of blood (× 10^9/l)

Question 8

RBC units

Answer 8

RBC – red blood cell count in a given volume of blood (× 10^12/l)

Question 9

Hb units

Answer 9

g/L

Question 10

PCV units / Hct units

Answer 10

PCV=Hct same thing.

L/L (litres of RBC per litres of blood)

Question 11

MCHC units

Answer 11

g/L

Question 12

platelet units

Answer 12

(× 10^9/l) , same as WBC

Question 13

what parameter does staining correlate with

Answer 13

MCHC (concentration of Hb per RBC)

Question 14

What is polycythaemia

Answer 14

abnormal increased Hb conc/RBC no.

Question 15

types of polycythaemia

Answer 15

1. Pseudo/apparent polycythaemia - reduced plasma volume

2. True polycythaemia - increased RBC volume

Question 16

Causes of true polycythaemia

Answer 16

1. Blood doping/ overtransfusion
2. Normal response due to increased EPO, eg hypoxia will cause a physiological increase in EPO
3. inappropriate EPO eg EPO from a kidney tumour
4. Intrinsic problem with the bone marrow leading to increased RBC in blood. this is called Polycythaemia vera/ primary polycythaemia. ie a problem independent of EPO stimulus

Question 17

When during the human development is RBC, Hct and Hb the highest?

Answer 17

Neonates (first 28 days after birth) have higher RBC, Hct and Hb than other times of life

Question 18

Men vs Women, Children vs Adults, who has higher RBC Hct and Hb

Answer 18

Men>women

Adults>children (not neonates)

Question 19

define Myeloproliferative Neoplasms

Answer 19

When body produces too much of the myeloid lineage cells, including WBC, RBC and platelets.

Question 20

Name a consequence/complications of polycythaemia

Answer 20

Thick blood/hyperviscosity

=> vascular obstruction

Question 21

Treatment of polycythaemia

Answer 21

1. If there is no physiological need for a high haemoglobin, or if hyperviscosity is extreme, blood can be removed to thin the blood
2. If there is intrinsic bone marrow disease (polycythaemia vera) drugs can be used to reduce bone marrow production of red cells