PCV.pptx

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, 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

8. Color Condition Clear\straw Normal Yellow Jaundice Opaque\turbid Hyperlipidemia Pink\red Hemolysis Conditions causing changes in appearances of plasma

9. 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.

10. 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.

11. 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)

12. Causes of Increased PCV polycythemia Dehydration Kidney & heart problems Diarrhea Burns smoking

13. Decreased PCV is seen in Anemia Pregnancy Hemolysis