Equations

Question 1

What is the equation for a corrected bleed

Answer 1

multiply the ratio of foetal cells/mothers cells by 2400 to give your answer in mls

Question 2

What is the equation for the mean corpuscular volume?

Answer 2

(Hct% x10)/ RBC

Question 3

What is the equation for mean corpuscular haemoglobin?

Answer 3

Haemoglobin/RBC

Question 4

What is the equation for MCHC

Answer 4

Hb x 100/ Hct %

Question 5

Equation for using a haemocytometer to count wbcs
(4)

Answer 5

Count the wbcs you see in the four outer corners of the haemocytometer

Add them all together to give you N

(N x 20)/ 0.4 ul = ul

(N x 20 x 10^6) / (0.4) = L

Question 6

What is the equation for absolute reticulocyte count?

Answer 6

(% reticulocytes/100) x RBCC

Question 7

How do you work out% reticulocytes

Answer 7

Miller square
- Count all the reticulocytes in the big box
- Count all the cells in the small box
- Keep doing this till you have about 115 cells counted in the small box
- Multiply small box by 9 = N

N = number if red cells counted

% Reticulocytes = Reticulocytes counted (big box)/ No of red cells counted) x 100

Question 8

How do you use your thin film to determine % parasitaemia

Answer 8

Use the Miller square to count:

• the number of parasite cells inside the big square
• the number of non-infected rbcs in the small square

(infected cells/ (non-infected x 9)) x 100

Question 9

What is the equation for the Rosner Index

Answer 9

(1:1 mix clotting time result - NPP clotting time result)/ initial prolonged clotting of patient sample