Measurement and clinical significance of hematocrit or packed cell volume

HCT PCV TEST

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

Microhematocrit 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.
microhematocrit method
microhematocrit method
PCV measurement
PCV measurement

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.
Also read  How to stain peripheral blood and interpret blood film (Giemsa stain)

Automated method

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.

Automated hematology analyzer
Automated hematology analyzer

PCV/HCT Normal Range

PCV(L/L)HCT(%)
MEN 0.45±0.05L/L45±5%
WOMEN 0.41±0.05L/L41±5%

Clinical Significance of PCV/HCT

Reduced HematocritMostly seen in anemic condition
Increased hematocrit seen in polycythemia

Also Read : Red Blood Cell Indices (MCV,MCH and MCHC) Clinical Significance

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About the Author: Arthur Westmann

DEFFE ARTHUR (AMOEBAMANN) is the founder and author of MLTGEEKS and MLTEXPO.He’s from Cameroon and is currently a Final year State Medical Laboratory Technician (MLT MA). Beyond lab works, he’s a passionate internet user with a keen interest in web design and blogging. Furthermore He likes traveling, hanging around with friends and social networking to do in his spare time.

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