Packed Cell Volume (PCV) Test Procedure: Hematocrit:

APPARATUS:

Wintrobe’s tube with stand, 2 ml disposable syringe with needle, Pasture pipette, mixture of double oxalate, centrifuge machine and spirit swab.

PRINCIPLE:

Anticoagulant mixed blood is filled in a tube and centrifuged. Cells settle down towards the bottom because of their greater density leaving the clear plasma on upper side. Percentage of volume of cells in total blood is known as packed cell volume (PCV).

PROCEDURE:

Following is the procedure of determining of packed cell volume.

• Centrifuge the blood in centrifuge machine at 3000 revolutions per min for 30 minutes.
• Draw 2 ml of blood from the vein with all aseptic measures and eject the blood in the vial after removing the needle from the syringe. Mix the blood with anticoagulant gently.
• Take powdered mixture of double oxalate (ammonium oxalate 3 mg and potassrum oxalate 2mg) in a clean and dry glass vial.
• Fill the Wintrobe tube with the help of Pasture pipette upto the mark 100 mm.
• Three layers are formed:

1. Clear plasma in upper part of tube.
2. Buffy coat layer (in between two layers).
3.  Red cells (red column) in lower part of tube.

• Packed cell volume is read directly from the calibration of tube from bottom to upper end.
• Buffy layer: Grayish white layer about 1 mm size on the u er end of red I consists of WBC and platelets.

Normal Value:

Adult man: 45% (40-50%)

Adult woman: 42% (37~47%)

Precautions:

1. there should be no air bubble or froth of blood in the tube.
2. Always use double oxalate as anticoagulant.
3. Wintrobe’s tube should be clean and dry.

Variation in Packed Cell volume:

Increase in Packed Cell Volume:

Physiological.

• Newborn and infants .
• High altitude (secondary polyethemia).
•  Higher in man as compared to woman.

Pathological.

• Spherocytosis.
• Hypoxia.
• Polycythemia.
• Dehydration.

Decrease in Packed cell volume:

Physiological.

• Less in woman than man.
• Pregnancy.

Pathological.

• Anaemia.
• Bone marrow depression.