MEASUREMENT OF PACKED CELL VOLUME (PCV)
This is the measure of the relative mass of erythrocytes present in a sample of a whole blood.
AIM: The packed cell volume or haematocrit is used to calculate the mean cell volume (MCV). These red cell indices are used in the investigation of anaemia
SPECIMEN: Well mixed, welll oxygenated EDTA anti-coagulated blood or capillary blood can be used.
EQUIPMENTS REQUIRED:- Micro-haematocrit centrifuge -capillary tubes, sealant.
PRINCIPLE; The Red blood cells in the capillary tube are separated by centrifuge force of gravity.
Using a heparinized capillary (red tipped); collect a capillary blood filling 3/4 of the tube.
Seal the unfilled end using a sealant material or heat seal the capillary using a small flame from a spirit lamp or pilot flame of a Bunseii burner, rotating the end of the capillary in v the flame until it. get bulk end.
Carefully located the filled capillary ion one of the numbered slots of the micro-haematocrit rotor with the sealed end against the rim gasket (to prevent breakage).
Write the number of the slot on the patients form. Position the safety cover and the lid carefully to avoid dislodging the tubes.
Centrifuge for 12,000 revolution per min (10,000 rpm) for it< Sminutes
Immediately after centrifuge, read the PCV making sure that there has been no leakage of blood from the capillary or breakage.
HOW TO READ PCV PCV is read using Hand-held micro-haematocrit reader Position the tube in slot so that the base line of the reader (zero line) interests base of red cell.
Move tube holder so that the top line (hundred ' line) interests top of plasma.
Adjust knob so that the middle line interests top of red cells.
Read the percentage of PCV on the scale.
HOW TO READ PCV WHERE THERE IS NO READER
Use a ruler to measure the height of the total column of blood (top of plasma to bottom of red cell column) in rnrn.
Read out the height of the cell column
Then calculate the PCV.
Thus PCV = Height of red cells column (mm) height of total column (mm)
Example: If the height of the packed cell whole sample in mm are 19mm and 49mm respectively, then the PCV can be obtained-using the above as follows.
PCV =19 = 0.388L Packed cells/L Whole blood
49 = 39%
Packed cell volume is expressed in percentage (%) and it is age, gender and altitude dependent it's accuracy can be affected by Specimen collection
The quality of capillary tube used
The time and speed of centrifuge
Method used for reading the result The reference ranges includes:
Adult male 40- 54%
Adult females 36 - 47%
Infants 44 - 64% •
WHITE BLOOD CELL COUNTS
AIM: A white cell count (WBC) is used to investigate infections and unexplained fever and .to monitor treatments which can cause leucopoenia
SPECIMEN: EDTA anti-coagulate blood sample or capillary blood samples can be used.
EQUIPMENT: Counting chamber (Haemacytorneter), Counting Chamber cover glasses, pipettes, Hand counter.
READGENT: WBC diluting fluid such as Turks solution
Turks solution: Is made up of 2mls of Glacial acetic acid 98mls of water tinge with
PRINCIPLES: The ting
- Count the cells in the four large corners squares of the chamber and also the cells lying on the lines of two side of each large square.
Report the number of white blood cells per liter of blood using this method.
If you count four large squares, multiply the sum of the four squares by 50.
If you count two adjacent large squares, multiply the sum. of the tow squares by 100.
After performing the count, before the sample dries, dismantle the chamber, wash and dry it.
Store it with the cover glass in a safe place.
White blood cell count is expressed in cell/mm3 and normal 'ranges varies with age and gender. Its references ranges includes:
Children at 1 year 6,000 - 18,000 cellls/mrn3
Children at 4-7years 5,000 - 15,000 cells/mm3
Adults 4,000 - 10000 cells/rnrn3
Raised WBC (Leucoytosis) could be as a result of
Poisoning etc. Reduced WBC (Leucopenia) could be as result of
Viral, Bacterial or parasitic infections e.g. HIV/AIDS
Vitamin 612 deficiencies