red blood cell count

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Red Blood Cell Count

Red Blood Cell CountBy: Shefaa Adel Hejazy.

Umm Al-Qura University, Makkah.Faculty of Medical Sciences. Hematology Dept.1st Semester 1433/2012

Red Blood Cell = Erythrocyte RBC is a flexible cell, biconcave disc in shape, and around 8 m in diameter.

The number of red cells per volume of blood, measured in microliters (L) or cubic millimeters (mm3)

Why do we count RBCs?

Counting of RBCs can be performed either:

Automated Method: (Electronic hematology cell counter, e.g. COULTER)


Manual Method: (visual using a microscope and counting chmber), which is a cumbersome and less accurate.

The solution used for red cell count is Isotonic with RBCs; doesnt lyse leukocytes.

Leukocytes are normally too few which can be identified easily and wont be interfered with erythrocytes count.

Reagents and instruments:

1. Neubauer Chamber (Haemocytometer) & coverslips.

2. RBC diluting fluid/solution.Consists of 3.2 g of Na-citrate and 1.0 ml of formaldehyde solution made up to 100 ml with D.W.



Haemocytometer (Manual method)

Improved Neubauer Chamber H


A thick glass slide with H shaped moats in it.

The area between two lines of H (center) is 0.1 mm in depth.

Moat prevents mixing of 2 samples on either side of chamber.



Prepare a plastic tube (labeled). Prepare 1:200 blood dilution (4 ml of diluent + 20 l Blood).

So, add diluent to the tube. Mix the sample (5 times); then aspirate 20l and transfer to the tube and mix.

Clean the Haemocytometer and coverslip with 70% ethanol followed by D.W &Leave to dry.

Place a coverslip on the Neubauer chamber.


Then, fill the chamber with the diluent (10 microliter) in each side.Leave chamber in humidity (petri-dish with wet filter paper) for 1-2 min. !?

Condenser slightly lowered. Iris diaphragm should be almost closed.

Place chamber on microscope stage. Start with 10X to focus; then with 40X count RBCs.


How to count RBCs?RBCs should be counted in the central square of the chamber.

Select 5 small squares (One at each corner and one in the center).

WWWWRBCAreas for WBCs and RBCs count


WRAreas for WBCs and RBCs count

3 mm.sq

25 smallSquares = 1 mm.sq


Areas for WBCs and RBCs countWBCsRBCs

Central large square

Count all cells in specified squares, and multiply by the proper conversion factor; the number of cells per cubic millimeter can be determined.

Count all cells within 16 squares and those lying on middle lines, EXCEPT

How to count ?

RBCs (1012/L) = No. of RBCs counted X Dilution X 106

Volume (l)

Dilution = 200

Depth of the chamber = 0.1 mm.

Volume of 5 small squares = 0.02 l

So, Red cell count/ liter = N x 0.01 x 1012 i.e. RBCs= N x 1012/L Calculations


Diluent should be correct.

No overflow in the moats. No air bubbles and debris in the chamber area.

No scratches in the ruled area of the chamber.

Pipettes used must be clean and dry.


RBCs Reference values:

RBC countAge group4.7 6.1 X 1012 /LAdult Male4.2 5.4 X 1012 /LAdult Female4.4 -5.8 X 1012 /L Newborn3.8 5.5 X 1012 /L Infant/ children


Interpretation of ResultsDecreased value ( RBCs)

Anaemia: due to Blood loss, production of cells, destruction of cells, and dietary insufficiency.

Diseases which affect the Bone Marrow such as:

LeukaemiaMMHodgkins Lymphoma

Subcutaneous bacterial endocarditis

Rheumatic fever

Increased value ( RBCs)

Polycythaemia vera

Secondary polycythaemia, e.g. smokers, high altitude, cyanotic heart defects, and COPD.


Acute poisoning

Severe diarrhea

Interpretation of Results

Good Luck


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