This document describes the microhematocrit method for determining hematocrit (Hct), which is the volume percentage of red blood cells in whole blood. The microhematocrit method involves filling capillary tubes with anticoagulated whole blood, sealing one end, and centrifuging the tubes for 5 minutes at 10,000 rpm. After centrifugation, the hematocrit reading is taken where the boundary between red blood cells and plasma intersects the microhematocrit scale. Normal Hct ranges are provided for different groups. Proper technique and avoiding sources of error like incorrect anticoagulant or centrifugation are emphasized for obtaining accurate Hct results.

1. Hematocrit determination
Hussein A. Abid 
Lecture: 03
Middle Technical University
Technical Institute of Baquba
Medical Laboratory Technology Department
Academic year 2019-2020 – Spring semester
Medical Laboratory Technology & Quality Control Applications
Module code: MLT113
L.No.: MLT113-20-T-03

2. What is hematocrit (Hct)?
• The volume of the red cells per unite volume of
blood.
Or
• The percentage volume of red cells in a volume
of whole blood.
• Also called ‘‘packed cell volume’’ (PCV).
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3. The packed cell volume can be
estimated by:
1. Macro-method (Wintrobe’s method)
2. Micro-method (microhematocrit)
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4. Micro-method
1. Principle:
 Hct is usually determined by spinning method
using a blood filled capillary tube in a centrifuge
machine.
 The coulter counter series of analyzers provide
an indirect measurement of haematocrit.
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5. Micro-method
2. Procedure (reagents & instruments):
 Capillary tubes, plain (75 mm)
 Micro-haematocrit centrifuge
 Micro-haematocrit reader
 Haematocrit tube sealant
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6. Micro-method
2. Procedure (sample):
 Capillary and venous blood in anticoagulated EDTA
tube or directly collected and used blood
2. Procedure (step-by-step):
A. Mix the anticoagulated venous or capillary blood
gently 5 times.
B. Fill (2/3) the capillary tube with blood (prefer to use
two tubes for each sample).
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7. Micro-method
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8. Micro-method
2. Procedure (step-by-step):
C. Seal one end of the tube with plasticine (sealing
wax), and place these tubes in the micro
haematocrit centrifuge.
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9. Haematocrit centrifuge
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10. Haematocrit centrifuge
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11. Micro-method
2. Procedure (step-by-step):
D. Centrifuge for 5 minutes at (10,000 rpm).
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12. Micro-method
2. Procedure (step-by-step):
E. Place the tube in micro-haematocrit scale.
F. The bottom margin of red cells layer is against
the 0 mark of the scale; While the top margin of
plasma layer should be facing the 100 mark.
G. Now adjust the sliding line so that it cuts between
the red cell layer and the buffy coat.
H. Note the reading. This is PCV (%).
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13. Micro-method
2. Procedure (step-by-step):
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micro-haematocrit scale

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Normal ranges of Hb
Hematocrit (%) PCV (L/L)
Newborn 53 – 65 0.53 – 0.65
Infant/child 30 – 43 0.30 – 0.43
Adult male 42 – 52 0.42 – 0.52
Adult female 37 – 47 0.37 – 0.47

15. Precautions
• Incomplete sealing of the capillary tubes will give falsely
low results.
• Shortened spin time or slowed centrifugation speed may
yield falsely elevated results.
• Micro-haematocrit centrifuge should never be forced to
stop by applying pressure to the metal cover plate.
• The haematocrit is usually three times the haemoglobin.
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16. Source of error
 Incorrect anti-coagulant concentration.
 Incorrect mixing.
 Storage for 6-8 hours.
 Incorrect centrifugation.
 Hemolysis.
 Clots in the blood sample.
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17. 16
Decreased Hb
Anaemia
Pregnancy

18. 17
Increased Hb
Newborn
High altitudes
Dehydration
Burns