Felis ISSN 2398-2950

Hematology: packed cell volume

Synonym(s): PCV, Hematocrit

Contributor(s): Karen L Gerber, Andy Torrance

Overview

  • 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.
  • Packed cell volume (PCV) is calculated from a spun sample, hematocrit is usually calculated by automated counters from cumulative cell volumes of counted red blood cells (RBCs).

Sampling

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Tests

Methodologies

Wintrobe method

  • Hematocrit tube of uniform bore calibrated longitudinally into 10 cm or 100 mm. Numbers on the right read from 0 to 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 minutes Centrifuge .
  • 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 minutes at 10,000 rpm or 2 minutes 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.

Availability

  • Widely available.

Validity

Sensitivity

  • Very sensitive.

Specificity

  • High.

Predictive value

  • Good.

Technique (intrinsic) limitations

  • Does not give direct information of red cell indices or of hemoglobin concentration.

Result Data

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Further Reading

Publications

Refereed papers

Other sources of information

  • Ettinger S J & Feldman E C (1995) Handbook of Veterinary Internal Medicine. Vol 2. p 1874.


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