RED BLOOD CELL COUNTING GENERAL PRINCIPLE The count

RED BLOOD CELL COUNTING GENERAL PRINCIPLE : The count of cells per volume unit is quite useful as diagnostic tool. . The only realistic alternative will be to use a counting chamber in which the cells are counted under the microscope.

GENERAL PRINCIPLE : � Depending on the kind of liquid to be analysed (expected cell number), a dilution and/or destruction of undesirable cells must be done. A simple calculation taking in accounting and it will give the number of cells per mm³.

GENERAL MATERIALS : Ø Hemacytometer {the counting chamber}. Ø Cover glass. Ø RBCs pipette with hose and Mouthpiece {Thoma red count pipette}. Ø Lancet needless (for drawing blood). Ø Platforms (for drawing blood). Ø Microscope. Ø 70% ethanol. Ø Bottle ringer's solution(a clear diluent for RBCs). Ø Absorbent paper.

Hemacytometer

Pipettes;

Procedure Set up all equipment on your desk so that you are sure to have everything at 1. Swab towards the side of the tip of a little-used finger with 70% Ethanol. 2. Lance by placing the platform of the auto let against the fingertip and pressing the trigger. 3. Using the dilution pipette with RED mixer from hemacytometer kit, draw blood up to the 0. 5 mark (Do not allow air to be drawn into the pipette or it will not draw the correct volume of blood, Do not allow blood to congeal in pipette Immediately proceed to the next step: �

Procedure 4. Continuing to hold the pipette as horizontal as possible, draw Ringer's solution diluent up to the 101 mark. (Dilution of 1 to 200. ) 5. Seal the tip with your finger and shake well to mix. 6. Empty ~1/2 of pipette into waste container add a small amount of the diluted blood to one chamber of the hemacytometer to just fill the chamber of the hemacytometer. (Do not over fill).

Procedure 7. Let the preparation sit for a minute (for cells to settle). 8. Center the grid at 100 x, switch to 400 x and count and record the RBCs in each of five fields(each with 16 smallest squares). Include in the count all cells touching left and bottom sides, ignore cells touching top and right sides. Calculate the RBCs/ mm 3 by adding the cells in the 5 groups and multiplying by 10, 000 (i. e. , add four zeros). RBCs/mm 3. 9. Wash out the pipette thoroughly with soap and water, rinse well, finish with distilled H 2 O.

Calculation: � Routinely, blood is drawn to the 0. 5 mark and diluted to the 101 mark with RBC diluting fluid. All the blood is washed into the bulb of the pipette (which has a volume of 100). Therefore, 0. 5 volumes of blood are contained in 100 volumes of diluting fluid. The resulting dilution is 1: 200.

N RBCs/mm 3 =----- x 400 x 200 x 10 80 � N = numbers of RBCs counted in {80 small squares}. � 80 = ( 5 x 16 ) small squares. � 400 = ( 16 x 25 ) total squares. � 200 = Dilution factor. � 10 = depth of the chamber.