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The Westergren technique measures sedimentation using a longer tube, allowing better discrimination between normal and abnormal values. International hematology guidelines recommend this method for routine clinical use.

Westergren Tube Characteristics

• Length: 30 cm

• Calibration: 0–200 mm

• Internal diameter: ~2.5 mm

• Orientation: Vertical during testing

Laboratories use either glass or plastic tubes, provided they meet calibration standards.

Anticoagulant Used

Sodium citrate (3.8%) serves as the standard anticoagulant in the Westergren method.

Blood-to-anticoagulant ratio:

• 4 parts blood

• 1 part sodium citrate

Proper mixing ensures uniform anticoagulation and prevents clot formation, which could falsely lower results.

Westergren Procedure

Laboratory professionals follow a standardized sequence to ensure accuracy:

1. Collect venous blood into a sodium citrate tube

2. Mix gently to avoid hemolysis

3. Fill the Westergren tube up to the zero mark

4. Place the tube vertically in a stable stand

5. Keep the setup away from vibration and direct sunlight

6. Record the fall of the red cell column after exactly one hour

Reading the result at eye level prevents parallax error and improves precision.

Reporting the Result

The laboratory reports ESR values in millimeters per hour (mm/hr).

Example:
If the red cell column falls 25 mm in one hour, the ESR equals 25 mm/hr.

Stages of Red Cell Sedimentation

Sedimentation occurs in three predictable phases:

1. Lag Phase (First 10 Minutes)

Red blood cells begin forming rouleaux stacks, resulting in slow settling.

2. Sedimentation Phase (Next 40 Minutes)

Rouleaux aggregates descend rapidly due to increased mass.

3. Packing Phase (Last 10 Minutes)

Cells pack at the bottom of the tube, slowing further descent.

Understanding these stages helps laboratory professionals recognize abnormal sedimentation patterns.

Factors Affecting ESR Values

Multiple variables influence ESR results, making careful interpretation essential.

Physiological Factors

• Advancing age

• Female sex

• Pregnancy

• Menstruation

Pathological Factors

• Anemia

• Infections

• Autoimmune disorders

• Malignancy

Technical Factors

• Tilted tube placement

• Incorrect anticoagulant ratio

• Vibrations

• High ambient temperature

• Delay in testing beyond two hours

Strict adherence to standard operating procedures minimizes technical error.

Normal ESR Values (Westergren Method)

Reference ranges may vary slightly by laboratory.

• Adult males: 0–15 mm/hr

• Adult females: 0–20 mm/hr

• Children: 0–10 mm/hr

• Elderly: Slightly higher values may occur

Clinical Significance of ESR

The Erythrocyte Sedimentation Rate plays an important role in long-term disease monitoring rather than acute diagnosis. In rheumatoid arthritis, ESR values often fall as treatment becomes effective. In tuberculosis, persistently high readings may suggest active disease or poor therapeutic response.

However, ESR alone never confirms a diagnosis. Clinical correlation remains essential.

High ESR: What It Indicates

Elevated ESR values commonly appear in:

• Acute and chronic infections

• Autoimmune diseases

• Chronic kidney disease

• Malignancies

• Severe anemia

• Pregnancy

Extremely high values demand immediate medical attention.

Low ESR: Clinical Relevance

Low ESR carries limited diagnostic importance. Conditions that increase blood viscosity or alter red cell shape typically produce reduced values.