Hematocrit is a frequently performed analysis in haematological laboratories for the evaluation of patients with anaemia.Hematocrit or packed cell volume (HCT / PCV) is defined as the volume occupied by red blood cells after the blood has been centrifuged at high speed.
Hematological Methods of Hematocrit estimation
It is measured by two methods thus
- The microhematocrit method
- Automated method
This is done using blood collected in EDTA and the equipments required for this method are
- Capillary tubes 75 mm in length with an internal diameter of 1mm.
- Microhematocrit centrifuge
- Reading device
Microhematocrit method Procedure
- Start by Placing the capillary tube in the venous blood sample which allows blood to enter the tube by capillary action. Leave the last 15mm of the capillary tube unfilled.
- Now seal the tube with modeling clay then make sure there is no air trapped between the clay and the column of blood.
- Place the tube in the microhematocrit centrifuge with the sealed end to the outer rim and centrifuge at 1500 rpm for 5 minute.
- Read the result using a microhematocrit reading device.
Significance of measuring hematocrit
- it is used as a screening test for anemia.
- Alongside with red cell count and hemoglobin evaluation, it is used for the calculation of red cell indices which are essential for classification of anemia.
- it can also be used as a reference method for calibrating automated hematology analysers.
- it provides a rough guide to Hemoglobin measurement and is very useful in the application of the Rules of Three
Some precautions when Measuring PCV/HCT
- The PCV test or HCT increases with storage so it must be measured within 6 hrs after sample collection
- The capillary tubes used must be of defined specifications.
- For speed and accuracy,Centrifuges must be checked at regular intervals.
This involves the use of automated machine for hematological analysis.This machine are known for their precision and accuracy with minimal effort.One of these machine used in Hematology is the Automated Hematology analyzer which is able to run Full Blood Counts and other hematological parameters.
PCV/HCT Normal Range
Clinical Significance of PCV/HCT
|Reduced Hematocrit||Mostly seen in anemic condition|
|Increased hematocrit||seen in polycythemia|