To Know
? What is Packed Cell Volume (PCV)
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? Methods for Determination of PCV (Hematocrit)? Clinical Importance of PCV (Hematocrit)
PCV
? PCV also known as Hematocrit is the volume
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occupied by Erythrocytes in the given volume
of
blood
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and
is
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usuallyexpressed
as
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percentage of the volume of the whole blood
sample.
Hematocrit (PCV)
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? Hematocrit is derived from Greek words `Haima'
meaning blood `krites' meaning to Separate. Together
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Hematocrit means `to separate blood'PRINCIPLE
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? Anticoagulant mixed blood is filled in a tube and
centrifuged.Cells settle down towards the bottom
because of their greater density leaving the clear
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plasma on upper sidePROCEDURE
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? Under aseptic condition get a venous blood sample.
? Carefully mix the blood with anticoagulant (Ammonium oxalate 3mg
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and Potassium Oxalate 2mg) in a tube by repeated inversions.? Fill the Wintrobe tube with the help of Pasteur pipette to the 10cm
mark. Which represents 100%.
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? Place the Wintrobe tube in the centrifuge machine and other Wintrobe
tube filled with water on the opposite side so as to balance it.
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Precautions
? There should be no air bubble or froth of blood in the tube.
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? Always use double oxalate as anticoagulant.
? Wintrobe tube should be clean and dry.
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True hematocrit
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? After centrifugation small amount of plasma is still entrapped betweenRBCs.So the true Hematocrit is calculated as:
? Hematocrit
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96
True Hematocrit
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100Buffy Layer
? The buffy layer consists of packed platelets and leukocytes
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? Thickness 1mm? The thickness of buffy layer increases in leucocytosis ,leukaemia and
thrombocytosis
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Clinical ImportancePhysiologic (Normal) increase in PCV
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? New born and Infants? High altitude
? Higher in man as compared to female
Physiologic (Normal) decrease in PCV
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? Less in women as compared to man? Pregnancy ( hemodilution)