Deciding what is normal and interpreting blood counts

Question 1

What can the normal be affected by?

Answer 1

Age
Gender
Ethnicity 
Physiological status 
Altitude
Nutritional status 
Cigarette smoking 
Alcohol intake

Question 2

What is a reference?

Answer 2

carefully defined reference population

• normal is a vaguer concept

Question 3

How is the reference range determined?

Answer 3

Sample of healthy volunteers with defined characteristics , analysed , if Gaussian distribution take 2 standard deviations of each side and this will be 95% of the people who are normal.

WBC does not show Gaussian distribution

Question 4

How are WBC, RBC and platelet count determined?

Answer 4

Automated machine that counts the number of electrical impulses generated by cells flowing between a light source and a sensor.

Question 5

How was Hb determined?

Answer 5

By a spectrometer - converts haemoglobin to a stable form and measures light absorption.

Question 6

How is Hct determined?

Answer 6

Centrifuging a blood sample

Question 7

How is MCV determined?

Answer 7

Dividing the total volume of RBC by the number of RBC

Question 8

Compare MCH and MCHC:

Answer 8

Cells with low MCHC will appear less red

Cell can have normal MCH but low MCHC

MCH is the absolute amount of Hb in an individual RBC
MCHC is the conc of Hb in a RBC

MCHC is related to the shape of the RBC,