Hematocrit (packed cell volume) is the ratio of the volume of red cells to that of the whole blood. It indicates relative volume of red cells and plasma (e.g. in anemia red cells are reduced with corresponding reduction in the hematocrit) Methods Macromethod using Wintrobe tube • Micromethod using capillary tube • Automated analyse The packed cell volume is a measurement of the proportion of blood that is made up of cells. The value is expressed as a percentage

1. HEMATOCRIT

2. Introduction
• Hematocrit (packed cell volume) is the ratio
of the volume of red cells to that of the whole
blood.
• It indicates relative volume of red cells and
plasma (e.g. in anemia red cells are reduced
with corresponding reduction in the
hematocrit)

3. Methods of Estimation of
PCV
• Macromethod using Wintrobe tube
• Micromethod using capillary tube
• Automated analyser

4. WINTROBE TUBE
It is a special thick walled
• glass tube measuring 11 cm in length
• an internal diameter of 2.5 mm
• capacity of 1 ml.
• This is calibrated at 1 mm intervals from top as 0, 10, 20, 30,...100
for ESR and 100, 90, 80,...10, 0 for PCV.
• The markings are in descending order from the top for PCV
estimation.
Anticoagulants used: EDTA, dry heparin or double oxalate.

5. PRINCIPLE
• Anticoagulated whole blood is centrifuged at a
standard speed (3500 RPM). RBCs which are
heavier than white cells, platelets and plasma,
sediment at the bottom and the volume of red
cell mass denotes the hematocrit.

6. METHOD
• Collect the blood in an EDTA vial.
• Mix the blood sample properly so as to mix both plasma and cells.
• With the help of a Pasteur’s pipette (dropper with long,
thin capillary tube like nozzle)draw the blood from the
vial.
• Place the nozzle of pipette at the bottom of dry and clean
Wintrobe tube.
• Slowly press the rubber teat of the pipette and fill the tube till the
top mark of 100..

7. • Avoid any air bubble being trapped during filling of the tube.
• Centrifuge the tube at 3500 RPM for half an hour.
• Take the reading of packed red cells from bottom.
• It is expressed as percentage.
DIFFERENT LAYERS
• Lower layer: This consists of red blood cells (packed).
• Middle layer: It is also called buffy coat and is the thin red-gray layer between the red
cells and plasma consisting of WBC and platelets.
• Upper layer: This layer is composed of the plasma which is normally clear or straw colored

9. Color Condition
Clearstraw Normal
Yellow Jaundice
Opaqueturbid Hyperlipidemia
Pinkred Hemolysis
• Conditions causing changes in appearances of
plasma

10. • Buffy coat gives an approximate indication of the number
of WBCs (normally 0.1 mm of this layer = 1000 WBC/cu mm).
• Thickness of the buffy coat increases with marked
leukocytosis, as in CML, CLL and acute leukemias.
• Absent or minimal buffy coat implies leukopenia.
• WBCs and identification of abnormal cells is easier.
• LE cell test
• Note: Buffy coat is not useful for platelet estimation.
• Other use of Wintrobe tube is for ESR estimation.

11. Microhematocrit Method
• A heparinized capillary tube is used and the blood is filled by capillary action.
• One end is sealed and it is centrifuged in a special centrifuge.
• As the tubes are not graduated, the PCV is measured using a special chart.
Advantages
• Easy
• Small quantity of blood is needed (useful in pediatric patients).
• Less time
• Amount of plasma trapped in the red cell column is less, thereby minimizing the error.
Disadvantage
• It requires a special (expensive) centrifuge.

12. Automated Analyser
• Nowadays, automated analysers are available for estimation of hematocrit.
Normal range for PCV
• Hematocrit is expressed as a percentage (e.g. 45%) or as a decimal
fraction (e.g. 0.45).
• It is useful for evaluating absolute values like MCV and MCHC.
• Males 40-50%
• Females 36-46%
• Infants 45-70% (cord blood)

13. • Causes of Increased PCV
 polycythemia
 Dehydration
 Kidney & heart problems
 Diarrhea
 Burns
 smoking

14.  Decreased PCV is seen in
 Anemia
 Pregnancy
 Hemolysis