Hematocrit (HCT) or Packed Cell Volume (PCV)
● Hematocrit, also known as packed cell volume (PCV), is a measurement that indicates the percentage of red blood cells (erythrocytes) in the total volume of blood.
● It is commonly used to assess the oxygen-carrying capacity of the blood and to diagnose certain medical conditions.
● Hematocrit is the volume of packed red cells in a particular specimen of blood calculated as a percentage of the total volume of blood.
● Hematocrit (HCT) and packed cell volume (PCV) are used to measure red blood cell mass.
● It is generally a part of the complete blood count (CBC) test.
● The PCV test measures how much of the blood consists of cells.
● Hematocrit may be measured by centrifugation or automated methods.
● A PCV of 40% means that there are 40 milliliters of cells in 100 milliliters of blood.
● A calculated value obtained from modern automated hematology analyzers.
● It is the product of the mean cell volume (MCV) and the red blood cell (RBC) count, both of which are directly measured by the analyzer.
● The formula used to calculate the HCT is as follows:
HCT = (MCV x RBC count)÷10
Packed cell volume (PCV)
● This is a directly measured value obtained from centrifuging blood in a micro-hematocrit tube in a micro-hematocrit centrifuge.
● The PCV is measured as the height of the red cell column in a micro-hematocrit tube after centrifugation.
● It is the quickest and most readily available measure of the red blood cell component of blood
● Hematocrit is measured by centrifuging a blood sample in a narrow capillary tube.
● The blood components separate based on their densities, with red blood cells settling at the bottom, followed by a thin layer of white blood cells and platelets, and finally, plasma at the top.
● The height of the packed red blood cells is then measured and expressed as a percentage of the total blood volume.
● The hematocrit value is a valuable diagnostic tool in various medical situations.
● It helps in evaluating anemia, polycythemia (abnormally high red blood cell count), dehydration, and certain other blood disorders.
● It also aids in monitoring the response to treatment for anemia and assessing blood loss or fluid shifts.
Normal Ranges of Packed cell volume (PCV)
● Male adult: 42 –52%
● Female adult: 35 – 47%
● Pregnant females: 33- 38%
● Newborn: 42- 64%
● 1 – 5 years: 31- 44%
● 5 – 10 years: 35– 44%
● 11 – 18 years: 37 – 48% (male), 34 – 44% (female)
Indications of Packed cell volume (PCV)
● Hematocrit shows that a patient has anemia, erythrocytosis, or changes in plasma volume.
● Hematocrit value is used as a cutoff to determine the amount of requirement for transfusion.
Interpretation of Packed cell volume (PCV)
● Hematocrit is raised with an increase in the number of red blood cells or a decrease in plasma volume.
● Hematocrit falls in decreased erythropoiesis or hemolysis and hemorrhage where plasma volume is increased.
Increased Levels of Packed cell volume (PCV)
● Polycythemia vera
● Congenital heart disease
Decreased Levels of Packed cell volume (PCV)
● Bone marrow failure
● Hemolytic reaction
● Normal pregnancy
● Multiple myeloma
● Leukemia or lymphoma
● Nutritional deficiencies of iron or vitamin (B12 or
folate) and mineral deficiencies
● Recent or long-term blood loss
Interfering Factors of Packed cell volume (PCV)
Altitude: People living in high altitudes have a high HCT.
Pregnancy: Hemodilution of pregnancy causes decreased HCT.
Age: Lower HCT is seen in men and women over the age of 60.
Dehydration: Severe dehydration causes a false increase in HCT.
● A low hematocrit value may indicate conditions such as iron deficiency anemia, vitamin B12 or folate deficiency anemia, chronic inflammation, or blood loss.
● High hematocrit values can be seen in cases of polycythemia vera, lung disease, congenital heart disease, or dehydration.
● Although hematocrit provides valuable information about the blood’s composition, it does not provide a complete picture of the overall health.
● Other blood tests, such as hemoglobin levels and red blood cell indices, are often used in conjunction with hematocrit to provide a more comprehensive assessment.
● Hematocrit is commonly used in routine blood tests and can be interpreted alongside other blood parameters to aid in the diagnosis and monitoring of various conditions.
● Changes in hematocrit values over time can help healthcare professionals evaluate the effectiveness of treatments or interventions.
Nursing Implications of Packed cell volume (PCV)
● Manage fatigue avoid complications of anemia, maintain adequate nutrition, maintain adequate perfusion, and encourage compliance with prescribed therapy.
Also, Visit: Pathophysiology Notes