Erythrocyte sedimentation rate

Mr. Topesh Patle

AIM: Determination of Erythrocyte sedimentation rate (ESR)

Principle

  • The ESR is based on the principle of gravity and the aggregation tendency of erythrocytes.
  • In normal blood, erythrocytes have a negative charge, which causes them to repel each other and settle slowly.
  • However, the acute phase increases in the bloodstream when inflammatory processes occur.
  • These proteins cause erythrocytes to lose their negative charge and form rouleaux stacks, which settle faster due to increased density.
  • The ESR reflects the extent of inflammation, where a faster settling rate correlates with more inflammation.

 

Methods

Westergren Method

Materials Required

  1. Blood with sodium citrate
  2. Westergren tube
  3. Rack/Stand
  4. Pipette
  5. Timer

 

Procedure

  1. Blood Collection:
  • Collect 2 mL of venous blood from the patient and mix it with 0.5 mL of sodium citrate (3.8%) in a collection tube. The blood should be mixed gently to prevent clotting without causing hemolysis.
  1. Filling the Westergren Tube:
  • Place the anticoagulated blood in the Westergren tube, using a pipette, up to the zero mark (0 mm).
  • Ensure no air bubbles are present in the tube, as air bubbles can interfere with the accuracy of the reading.
  1. Placing the Tube in the Stand:
  • Place the tube vertically in the rack or stand. Ensure the tube is upright and undisturbed. Any tilting or movement can alter the sedimentation rate.
  1. Sedimentation Time:
  • Allow the blood to sediment for exactly 1 hour at room temperature (18-25°C). External factors like vibrations, temperature changes, or light exposure should be avoided during this time, as they may affect the result.
  1. Reading the ESR:
  • After 1 hour, measure the distance in millimeters from the zero mark to the top of the red blood cell column. This distance represents the ESR in mm/hour.
  • If sedimentation is unusually high or low, recheck the process for any errors or interference.

 

Normal ESR Values 

  • Men:
    • Under 50 years: 0-15 mm/hour
    • Over 50 years: 0-20 mm/hour
  • Women:
    • Under 50 years: 0-20 mm/hour
    • Over 50 years: 0-30 mm/hour
  • Children: 0-10 mm/hour
  • Newborns: 0-2 mm/hour
  • Pregnant women May show values up to 20-50 mm/hour, especially during the second and third trimesters due to physiological changes.

 

Wintrobe Method

Materials Required

  • Wintrobe tube
  • Anticoagulant: EDTA blood 
  • Rack/Stand
  • Pipette
  • Timer

 

Procedure

  1. Blood Collection:
    • Draw approximately 1-2 mL of venous blood from the patient into an anticoagulant (EDTA or sodium citrate) tube. Mix gently to avoid hemolysis or clotting.
  2. Filling the Wintrobe Tube:
    • Transfer the anticoagulated blood to the Wintrobe tube using a pipette to the ESR scale’s zero mark. Ensure no air bubbles are present, as this can affect the accuracy of the result.
  3. Positioning the Tube:
    • Place the Wintrobe tube vertically in a stand. Ensure the tube is perfectly upright because any tilt can affect the erythrocyte sedimentation rate.
  4. Sedimentation Time:
    • Leave the tube undisturbed at room temperature (18-25°C) for exactly 1 hour. External vibrations or temperature fluctuations should be avoided, as they can impact the sedimentation rate.
  5. Reading the ESR:
    • After 1 hour, measure the distance in millimeters that the red blood cells have fallen from the zero mark to the top of the column of red blood cells.
    • This distance represents the ESR in mm/hour.
  6. Recording the Results:
    • Report the result as the ESR in mm/hour. A higher sedimentation rate indicates a greater degree of inflammation.

 

Normal Values 

  • Men: 0-9 mm/hour
  • Women: 0-20 mm/hour
  • Children: 0-10 mm/hour

Advantages of the Wintrobe Method

  • Less blood required: This method is often used when a smaller blood sample is available (such as in pediatric patients).
  • Simultaneous hematocrit measurement: Using the same blood sample, the Wintrobe tube can also measure hematocrit (the proportion of blood that consists of red blood cells).

Disadvantages of the Wintrobe Method

  • Less sensitive to high ESR values: The shorter tube means this method is not as effective at measuring very high ESR levels (>100 mm/hour), making it less sensitive for detecting significant inflammatory processes.
  • Standardisation: The Westergren method is more commonly used and is better standardised, which is why many clinicians prefer it.

 

 

Clinical Significance

The ESR test is a nonspecific marker, meaning it cannot diagnose specific diseases, but it is a valuable indicator of the presence and extent of inflammation in the body. ESR values can be elevated or decreased in a wide range of conditions:

Elevated ESR (conditions causing faster red cell sedimentation)

  • Infections: Bacterial infections (e.g., pneumonia, tuberculosis), abscesses, and chronic infections.
  • Inflammatory diseases:
    • Autoimmune diseases (e.g., rheumatoid arthritis, systemic lupus erythematosus)
    • Vasculitis (e.g., temporal arteritis)
    • Inflammatory bowel diseases (e.g., Crohn’s disease, ulcerative colitis)
  • Cancers:
    • Malignancies (e.g., lymphoma, multiple myeloma, metastatic cancers)
  • Chronic diseases:
    • Chronic kidney disease
    • Endocarditis
    • Polymyalgia rheumatica
  • Pregnancy: Due to increased fibrinogen levels.

Decreased ESR (conditions causing slower red cell sedimentation)

  • Polycythemia: Increased number of red blood cells can cause a low ESR.
  • Sickle cell anaemia: The abnormal shape of red blood cells prevents rouleaux formation, resulting in decreased ESR.
  • Heart failure: Chronic heart conditions can sometimes result in a decreased ESR.
  • Hyperviscosity syndromes: Conditions that increase blood thickness, such as Waldenstrom’s macroglobulinemia.

 

Factors Influencing ESR

A wide range of factors, both physiological and pathological, influences ESR. Understanding these factors is essential for accurate interpretation of ESR results:

  1. Physiological Factors

  • Age: ESR tends to increase with age, especially in the elderly, due to physiological changes, even without disease.
  • Gender: Women typically have higher ESR values than men due to hormonal differences, especially during menstruation and pregnancy.
  • Pregnancy: ESR increases significantly in pregnancy, particularly during the second and third trimesters. This is due to increased fibrinogen levels and other physiological changes.
  • Menstruation: Due to hormonal variations, ESR may rise slightly during the menstrual cycle.
  • Haemoglobin concentration: Anemia can elevate ESR as there are fewer red blood cells, making it easier for them to form rouleaux and sediment faster.

  1. Pathological Factors

  • Inflammation: Acute-phase proteins (e.g., fibrinogen, C-reactive protein, immunoglobulins) produced during inflammation promote rouleaux formation, increasing ESR.
  • Infections: Bacterial and chronic infections significantly raise ESR due to the inflammatory response.
  • Chronic diseases: Conditions like rheumatoid arthritis, systemic lupus erythematosus, and malignancies can increase ESR due to chronic inflammation.
  • Cancer: Some cancers (e.g., lymphoma, multiple myeloma, metastatic tumours) cause elevated ESR due to the presence of cancer-related inflammation and tissue damage.
  • Kidney disease: chronic kidney disease can cause elevated ESR due to the buildup of inflammatory proteins and other metabolic factors.
  • Heart failure: Congestive heart failure can lower ESR, likely due to reduced fibrinogen levels and changes in blood viscosity.
  • Polycythemia: Increased red blood cells in polycythemia can reduce ESR because the cells crowd the plasma and hinder rouleaux formation.

  1. Technical and Environmental Factors

  • Tilt of the ESR tube: A tube that is not perfectly vertical will cause the red blood cells to settle faster, artificially elevating the ESR.
  • Temperature: ESR is temperature-sensitive. At higher temperatures, ESR may increase, while lower temperatures can slow sedimentation.
  • Sample processing time: ESR measurements must be taken within 2 hours of blood collection. Delayed measurement can cause falsely elevated ESR due to blood changes over time.
  • Tube size: The diameter and length of the ESR tube (Westergren vs. Wintrobe tubes) influence the sedimentation rate.
  • Clotting: Inadequate anticoagulation or improper mixing can cause clumping of red blood cells, falsely lowering ESR.