Erythrocyte Sedimentation Rate (ESR)

Practical: Determination of Erythrocyte Sedimentation Rate (ESR)

The erythrocyte sedimentation rate (ESR) is a laboratory test that measures the rate at which erythrocytes settle toward the bottom of a vertically positioned column of anticoagulated blood over a specified period.

ESR is a non-specific laboratory test. An increased ESR may occur in inflammatory, infectious, autoimmune, malignant, and other conditions. The result should therefore be interpreted together with the patient's clinical findings and other laboratory investigations.

Three methods commonly demonstrated in the laboratory are:

  1. Westergren method
  2. Modified Westergren method using a disposable ESR tube
  3. Rapid/fast ESR detection method

Method 1: Westergren Method

Principle

When anticoagulated blood is placed in a vertically positioned Westergren tube, erythrocytes progressively settle under gravity. During the initial phase, erythrocytes form rouleaux and subsequently sediment through the plasma.

The ESR is expressed as the height of the clear plasma column above the settled erythrocytes after 1 hour.

Reporting unit: mm/hour (mm/hr).

Requirements

  • Fresh venous blood
  • 3.8% trisodium citrate
  • Westergren ESR pipette/tube graduated from 0–200 mm
  • Westergren stand
  • Micropipette or appropriate filling device
  • Timer/stopwatch
  • Disposable gloves
  • Biohazard waste container

Specimen

Venous blood collected with 3.8% trisodium citrate in a 4:1 blood-to-anticoagulant ratio.

The specimen should be adequately mixed and tested as soon as practicable according to the laboratory's validated procedure.

Procedure

  1. Collect venous blood into the trisodium citrate tube using the appropriate blood-to-anticoagulant ratio.
  2. Gently mix the specimen by inversion. Do not shake vigorously.
  3. Fill the Westergren tube with the anticoagulated blood up to the 0 mm mark.
  4. Ensure that there are no air bubbles in the column.
  5. Place the tube vertically in the Westergren stand.
  6. Ensure that the stand is stable and located on a level surface free from vibration and excessive temperature variation.
  7. Start the timer immediately.
  8. Allow the blood to sediment undisturbed for 60 minutes.
  9. At exactly 60 minutes, read the level of the erythrocyte–plasma interface.
  10. Record the result as mm/hr.

Result

ESR = height of the erythrocyte sedimentation column after 60 minutes

Example:

Plasma column/erythrocyte interface = 18 mm
ESR = 18 mm/hr

Method 2: Modified Westergren Method Using Disposable ESR Tube

Principle

The modified Westergren method is based on the same fundamental principle as the conventional Westergren method. Anticoagulated blood is introduced into a pre-calibrated disposable ESR tube, which is positioned vertically. Erythrocytes settle under gravity, and the sedimentation distance is determined using the graduated scale.

Requirements

  • Fresh anticoagulated venous blood
  • Disposable ESR tube/pipette
  • ESR stand/rack compatible with the disposable tube
  • Appropriate anticoagulant according to the validated system
  • Timer/stopwatch
  • Disposable gloves
  • Biohazard waste container

Specimen

Use the specimen and anticoagulant specified by the particular disposable ESR system.

For a modified Westergren procedure based on citrate blood, use appropriately collected trisodium citrate-anticoagulated blood.

Procedure

  1. Collect venous blood into the appropriate anticoagulant tube.
  2. Gently mix the blood by inversion.
  3. Inspect the specimen for clot formation or inadequate filling.
  4. Transfer the required volume of blood into the disposable ESR tube using the manufacturer's recommended procedure.
  5. Fill the tube to the designated 0 mm/reference mark.
  6. Check for air bubbles and remove them if the manufacturer's procedure permits.
  7. Place the tube vertically in the appropriate ESR stand.
  8. Start the timer immediately.
  9. Keep the tube completely undisturbed during sedimentation.
  10. Allow sedimentation for the specified time of the validated disposable ESR method.
  11. Read the erythrocyte–plasma interface against the calibrated scale.
  12. Report the result according to the system's validated reporting procedure, generally as mm/hr when the system is calibrated to provide a conventional ESR value.
  13. Dispose of the used disposable tube and other contaminated materials as biohazardous waste.

Result

If the disposable tube is calibrated to provide a conventional Westergren-equivalent ESR:

ESR = ___ mm/hr

Method 3: Rapid/Fast ESR Detection Method

Principle

Rapid ESR systems are designed to obtain an ESR result in a substantially shorter period, commonly around 30 minutes, by using a validated tube configuration, measurement system, accelerated sedimentation procedure, or mathematical conversion.

The exact principle differs between commercial systems. Therefore, the manufacturer's instructions must be followed for the particular rapid ESR kit/instrument.

The final result from a system calibrated to provide conventional ESR is generally reported as:

mm/hr

The 30-minute measurement should not automatically be reported as mm/30 min.

Requirements

  • Fresh blood specimen
  • Anticoagulant specified by the rapid ESR system
  • Rapid ESR tube/cartridge/device
  • Compatible stand or analyzer
  • Timer, if required
  • Manufacturer-specified accessories
  • Personal protective equipment
  • Biohazard waste container

Procedure

  1. Collect the blood specimen according to the manufacturer's instructions.
  2. Mix the specimen gently by inversion.
  3. Prepare the rapid ESR tube/cartridge/device.
  4. Introduce the required volume of blood into the test system.
  5. Ensure that the specimen is correctly positioned and that there are no unacceptable air bubbles.
  6. Place the device in the appropriate stand or analyzer.
  7. Initiate the test according to the manufacturer's operating procedure.
  8. Allow the system to operate for the specified period, commonly approximately 30 minutes for rapid ESR systems.
  9. At completion, read the displayed or calibrated ESR result.
  10. Record the result in mm/hr when the system reports a conventional ESR-equivalent value.
  11. Dispose of the used tube/cartridge and contaminated materials as biohazardous waste.

Quality Control

Accurate ESR testing requires control of both pre-analytical and analytical variables.

Important quality-control measures

  • Use properly collected and adequately mixed blood.
  • Maintain the correct blood-to-anticoagulant ratio.
  • Reject clotted or grossly unsuitable specimens.
  • Use calibrated ESR tubes/pipettes.
  • Keep the tube strictly vertical.
  • Prevent vibration and mechanical disturbance.
  • Maintain appropriate environmental conditions.
  • Start timing immediately after the tube is positioned.
  • Read the result at the specified time.
  • Follow the manufacturer's instructions for disposable and rapid systems.
  • Perform equipment verification/calibration according to the manufacturer's recommendations.
  • Participate in appropriate internal quality control and external quality assessment (EQA) where available.

Interpretation

ESR is a non-specific marker of inflammation. An increased ESR may be associated with infections, autoimmune/inflammatory disorders, malignancies, anemia, pregnancy, and other conditions.

A normal ESR does not exclude disease, and an increased ESR does not establish a specific diagnosis.

Reference intervals vary with age, sex, pregnancy status, laboratory method, and population. Therefore, the laboratory's validated reference interval should be used rather than applying a single universal range.

Adult reference ranges are approximately:

  • Men: 0–15 mm/hr

  • Women: 0–20 mm/hr


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