🩸 Erythrocyte Sedimentation Rate (ESR)

A Key Blood Test in Laboratory Investigations

4

Introduction

The Erythrocyte Sedimentation Rate (ESR) is a common and simple blood test used in laboratory investigations to detect inflammation in the body. Although it is a non-specific test, ESR provides valuable information that helps clinicians diagnose, monitor, and manage various medical conditions.

What is ESR?

ESR measures the rate at which red blood cells (erythrocytes) settle at the bottom of a vertical test tube over one hour.

• The result is expressed in millimeters per hour (mm/hr).

• Faster sedimentation indicates the presence of inflammation or abnormal proteins in the blood.

When inflammation occurs, certain proteins (like fibrinogen) increase in the blood, causing red blood cells to clump together and settle more quickly.

Principle of the Test

The ESR test is based on three phases:

1. Aggregation Phase – Red blood cells form stacks (rouleaux formation).

2. Sedimentation Phase – Cells settle at a constant rate.

3. Packing Phase – Cells accumulate at the bottom of the tube.

Methods of ESR Measurement

1️⃣ Westergren Method (Most Common)

4

• Considered the gold standard.

• Uses a 200 mm calibrated tube.

• Blood is mixed with an anticoagulant (usually sodium citrate).

2️⃣ Wintrobe Method

• Uses a shorter tube (100 mm).

• Less sensitive than Westergren.

• Can also measure packed cell volume (PCV).

Normal Reference Values

Note: Reference ranges may vary slightly between laboratories.

Clinical Significance

🔺 Increased ESR May Indicate:

• Infections (bacterial, tuberculosis)

• Autoimmune diseases (e.g., rheumatoid arthritis, lupus)

• Inflammatory conditions

• Anemia

• Some cancers (e.g., multiple myeloma)

• Pregnancy

🔻 Decreased ESR May Be Seen In:

• Polycythemia

• Sickle cell anemia

• Severe leukocytosis

• Congestive heart failure

Advantages of ESR

• Simple and inexpensive

• Quick to perform

• Useful for monitoring chronic inflammatory diseases

• Requires minimal equipment

Limitations of ESR

• Non-specific (does not identify the exact cause)

• Affected by age, gender, anemia, and pregnancy

• Cannot replace more specific tests like CRP

ESR vs CRP

Role of ESR in Laboratory Investigations

ESR is commonly ordered as part of:

• Routine health checkups

• Investigation of unexplained fever

• Autoimmune disease workup

• Monitoring treatment response

• Chronic infection assessment

It is often interpreted alongside:

• Complete Blood Count (CBC)

• CRP

• Rheumatoid factor

• Other inflammatory markers

Conclusion

The Erythrocyte Sedimentation Rate (ESR) is a valuable screening tool in blood laboratory investigations. While it does not diagnose specific diseases, it plays an important role in detecting and monitoring inflammation. Due to its simplicity and affordability, ESR remains widely used in clinical practice worldwide.

🩸 How to Collect a Blood Sample for ESR (Erythrocyte Sedimentation Rate)

4

Collecting a proper blood sample is essential for accurate ESR results. Below is the standard laboratory procedure.

🧪 Specimen Required

• Venous blood

• Anticoagulant: 3.8% Sodium citrate (for Westergren method)
  OR

• EDTA blood (some laboratories use EDTA and then dilute accordingly)

🩺 Equipment Needed

• Sterile syringe or vacutainer

• Tourniquet

• Alcohol swab (70% isopropyl alcohol)

• Sterile needle

• Sodium citrate tube (black top ESR tube)

• Westergren pipette/tube

• ESR stand

• Gloves

📋 Step-by-Step Procedure for Sample Collection

1️⃣ Patient Preparation

• Explain the procedure to the patient.

• No fasting required.

• Ensure patient is relaxed and seated comfortably.

2️⃣ Venipuncture Procedure

1. Wash hands and wear gloves.

2. Apply tourniquet 3–4 cm above the venipuncture site.

3. Clean the site (usually antecubital vein) with alcohol swab.

4. Allow area to dry.

5. Insert sterile needle into the vein.

6. Collect required amount of blood (usually 2 mL).

3️⃣ Mixing with Anticoagulant

• For Westergren method:

  • Mix 4 parts blood + 1 part sodium citrate.

  • Gently invert tube to mix (do NOT shake).

Improper mixing can cause clotting and false results.

4️⃣ Filling the ESR Tube

• Fill the Westergren tube up to the “0” mark.

• Ensure:

  • No air bubbles

  • Tube is vertical

  • No blood leakage

5️⃣ Start Timing

• Place the tube upright in ESR stand.

• Start timer for 1 hour.

• After 1 hour, measure the distance (mm) the red cells have fallen.

• Report result in mm/hr.

⚠️ Important Precautions

• Perform test within 2 hours of sample collection.

• Keep tube strictly vertical.

• Avoid vibration during testing.

• Ensure proper anticoagulant ratio.

• Avoid hemolysis.

❌ Causes of Incorrect Results

• Clotted blood sample

• Tilted ESR tube

• Delay in testing

• Incorrect blood-to-anticoagulant ratio

• High room temperature

🧾 Summary