Haemocytometer
The counting of blood cells after proper dilution is known as
haemocytometry and the instrument used to count the blood cells is called
haemocytometer. Using haemocytometry method, red cells, platelets and eosinophils are often counted. Now-a-days it is also used for counting cells
of bacteria, yeast, or algae.
Haemocytometer – instruments description
A haemocytometer consists of a counting chamber, a coverglass for
the counting chamber and diluting pipettes. Many types of counting
chambers are available. Improved Neubauer and Fauchs Rosenthal are the
two most commonly used counting chambers in laboratories.
RBCs and WBCs in blood cannot be counted as such. The blood
has to be diluted in specific isotonic solutions. RBC, diluting fluid is called
Hayem’s solution. For WBC counting Turk’s solution or Toisson solution
can be used.
The total number of cells is expressed per mm3. The isotonic diluting
fluid keeps up the cells intact. In WBC counting, the solution will lyse the
red blood cells and the remaining nucleated WBCs are counted. Venous
blood is used in blood cells counting.
Normal Range of RBCs in human is as follows
Men : 4.5 – 5.9 million/mm3
Women : 4.1 – 5.1 million/mm3
At birth : 4.0 – 5.6 million/mm3
Normal Range of WBCs in human is as follows :
Adults : 4,500 – 11,000/mm3
Neonates : 10,000 – 25,000/mm3
Clinical significance :
1. Decrease in the number of circulating erythrocytes indicates anaemia.
2. An increased number of erythrocytes indicates the possibility of
polycythemia.
3. An increase in WBC count for a transient period indicates bacterial
infection.
4. Progressive increase in abnormal WBC count indicates the possibility of
leukemia.
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