Deciding what is normal and interpreting a blood count

Question 1

How is a reference range derived? How does a normal range differ?

Answer 1

RR = Derived from a carefully defined reference population
Healthy pop
defined characteristics
analysed with instrument/ technique used for patients

Question 2

How does a normal range differ from a reference range?

Answer 2

Much vaguer

Question 3

What statistical technique is used to decide what is normal?

Answer 3

Gaussian

Question 4

How is the Gaussian distribution determined?

Answer 4

Mean +/- 2SD as 95% range

Question 5

What 2 caveats are given with a 95% range?

Answer 5

Not all results outside the RR is normal

Not all results inside the RR are normal

Question 6

What units are used for MCV?

Answer 6

fl

Question 7

What units are used for MCHb?

Answer 7

pg

Question 8

What units are used for MCHC?

Answer 8

g/l

Question 9

What units are used for platelet count?

Answer 9

x10^9/ l

Question 10

How is MCV calculated? (old and new methods)

Answer 10

Old: Total volume of red cells/ number of red cells
New: determined by indirect light scattering/ interruption of an electric field