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SOP

Packed Cell Volume (Microhematocrit)

SOP for determining the percentage of whole blood volume occupied by red blood cells using centrifugation.

Last verified 1 month ago 2 min read Haematology Manual Haematology Laboratory Techniques #Haematology #PCV #Hematocrit #microhematocrit #centrifugation #red blood cells
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Document Control
Version
1.0
Effective
Aug 29, 2026
Reviewed
Aug 29, 2026
Department
Hematology
Principle

When whole blood is subjected to high-speed centrifugation, the denser cellular components (primarily red blood cells) are forced to the bottom of the capillary tube, while the less dense plasma remains at the top. A thin white layer (buffy coat) of WBCs and platelets forms between them. The PCV is the ratio of the height of the RBC column to the total height of the blood column.

Standard Operating Procedure: Packed Cell Volume (PCV)

1. Purpose and Scope

To determine the volume percentage of red blood cells in whole blood using the microhematocrit centrifugation method.

2. Specimen Requirements

  • Type: Whole blood.
  • Anticoagulant: K2/K3 EDTA or capillary blood (heparinized tube).
  • Stability: Test within 6 hours at room temperature.
  • Rejection: Clotted samples.

3. Safety and Precautions

  • Standard PPE. Ensure centrifuge lid is securely locked before starting.

4. Equipment and Reagents

  • Microhematocrit centrifuge.
  • Capillary tubes (plain for EDTA blood, heparinized for capillary blood).
  • Tube sealant (clay/plasticine).
  • Hematocrit reader.

5. Step-by-Step Procedure

  1. Mix the EDTA specimen gently by inverting 8-10 times.
  2. Fill a capillary tube to about 3/4 of its length by touching it to the blood drop or dipping it into the EDTA tube.
  3. Wipe the outside of the tube clean.
  4. Seal the dry end of the tube firmly with sealing clay. Ensure a flat, leak-proof seal.
  5. Place the tube in the centrifuge rotor with the sealed end pointing outward (against the rubber gasket). Balance with an opposite tube.
  6. Secure the inner and outer lids. Centrifuge at 10,000-12,000 RPM for 5 minutes.
  7. Remove the tube and place it in the hematocrit reader.
  8. Align the bottom of the red cell column with the 0% line and the top of the plasma with the 100% line.
  9. Read the percentage at the top of the red cell column (excluding the buffy coat).

6. Quality Control

  • Check centrifuge speed with a tachometer every 6 months.
  • Ensure no plasma is trapped in the red cell column (recentrifuge if PCV > 50% to rule out trapped plasma).

7. Reference Ranges

  • The canonical sex-specific adult reference intervals are shown in the Reference Ranges panel below.

8. Reporting Results

  • Report as a percentage (%) or decimal fraction (L/L).

Reference Ranges

Browse all ranges

40.7–50.3 %

Critical values apply

36.1–44.3 %

Frequently Asked Questions

Centrifugal force pushes the denser red blood cells toward the outside of the rotor. If the sealed end is inward, the cells will push against the seal, potentially causing it to leak and ruining the sample.
The buffy coat is the thin white layer of white blood cells and platelets. It must NOT be included in the PCV reading; the reading is taken at the top of the red cell column.