ISSN 2398-2942      

Hematology: packed cell volume


Kathleen P Freeman

Synonym(s): PCV, Hematocrit


  • High speed centrifugation separates layers of cells:
    • Erythrocytes.
    • Buffy coat (thrombocytes, leukocytes and nucleated erythrocytes).
    • Plasma.
  • Measurement of these components indicates the patient's erythrocytic and hydration status.
  • PCV is calculated from a spun sample, hematocrit is usually calculated by automated counters from cumulative cell volumes of counted RBCs (Calculated hemocrit (%) = MCV (fl) x RBC (x10*12/l)/10).
  • Relationship of Hbg and PCV: Hbg x 3 = PCV.
  • Relationship of RBC and PCV: PCV / 6 = RBC. Is not valid when disease is present.


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Wintrobe method

  • Hematocrit tube of uniform bore calibrated longitudinally into 10 cm or 100 mm. Numbers on the right read from 0-10 cm and are used to determine PCV. Numbers on the left are used for erythrocyte sedimentation rate.
  • Fill the tube to the 10 cm mark with a well-mixed sample of blood in anticoagulant, ensuring that there are no bubbles.
  • Centrifuge sample at 3000-4000 rpm for 30 min.
  • The scale is then read at the top of the packed erythrocytes adjacent to the buffy coat. The number is multiplied by 10 to express PCV as % (SI units → expressed as l/l).

Microhematocrit method

  • Fill a plain capillary tube with anticoagulated blood to 1 cm from the end and wipe the outside of the tube. Seal the vacant end of the tube with clay, plastic or by heating. If blood is taken directly from the animal (ear tip, nail, etc), use heparinized tubes.
  • Using a microhematocrit centrifuge, spin for 5 min at 10,000 rpm or 2 min at 16,000 rpm.
  • Read the PCV using one of a variety of microhematocrit readers.
  • Advantages: small volume of blood required, quick to perform.
  • Automatic counters calculate the hematocrit from the cumulative volume of the cells counted.
  • Standardize technique using microhematocrit method.
  • Adequate centrifugal force and time of centrifugation required for maximal cell packing and minimization of trapped plasma (5 min usually adequate for canine blood).
  • Measure height of packed erythrocytes relative to total height at top of plasma column.

Calculated hematocrit (larger commercial analyzers) Q-BC technique


  • Widely available at commercial laboratories.
  • Facilities to measure PCV should be available in all practices.



  • Moderate to high.


  • Low.

Predictive value

  • Good.

Technique (intrinsic) limitations

  • Does not give direct information of red cell indices or of hemoglobin concentration.
  • Highly repeatable and accurate with trained staff and/or commercial equipment.

Technician (extrinsic) limitations

  • Requires practice to accurately read microhematocrit tubes.

Result Data

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Further Reading


Refereed papers

Other sources of information

  • Cowell R J, Tyler R D & Meinkoth J H (1999) Diagnostic Cytology and Hematology of the Dog and Cat. 2nd edn. Mosby, USA.
  • Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine Clinical Pathology. 3rd edn. Iowa University Press, USA.
  • Jain N C (1993) Essentials of Veterinary Hematology. Lea & Febiger, USA.


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