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Erythrocyte sedimentation rate (ESR): principle, method, procedure and clinical application

Principle of ESR:

When an anticoagulant is added to the blood and this well mixed venous blood is placed in a vertical tube, erythrocytes tend to settle towards bottom leaving clear plasma on top. This rate of sedimentation of red blood cells in a given interval of time is called erythrocyte sedimentation rate (ESR).

As the erythrocytes sediment, in a period of one hour, 3 stages can be observed.

  1. Stage I: first 10 minutes
    1. It is initial period of aggregation during which rouleaux are formed and the sediment rate is low
  2. Stage II: next 40 minutes
    1. It is a period of fast setting. Sedimentation occurs at a constant rate during this period
  1. Stage III: next 10 minute or more
    1. The sedimentation again slows as it is the final period of packing of cells at the bottom of the tube


Factors affecting ESR:

  1. There are several factors that affects sedimentation of erythrocytes.

  2. Factors that increase ESR:

    1. Anemia:
      1. anemia increase ESR because the change in erythrocyte-plasma ratio favors rouleaux formation.
      2. Rouleaux is aggregation of RBCs together due to their discoid shape.
      3. Rouleaux have a decrease surface area and accelerate ESR
    2. Increase level of fibrinogen:
      1. it decreases the negative charge of erythrocyte, so RBC tend to remain apart and this promotes formation of rouleaux and increase ESR
    3. Immunoglobulin:
      1. increase antibody level in blood increase ESR
    4. Increase cholesterol level
    5. Rheumatoid arthritis
    6. Chronic infections
    7. Carcinoma
    8. Tissue destruction and other disease

  1. Factors that decrease ESR:

    1. Defibrinigenation:
      1. removal of fibrinogen decreases ESR
    2. Increase albumin and lecithin in blood
    3. Abnormal or sickle shape RBCs:
    4. abnormal or irregular shape of RBC lower ESR
    5. Congestive heart failure


Method for ESR estimation:

Westergren method for ESR estimation is widely used method. Wintrobe method is also used for ESR determination. Wintrobe tube is smaller than westergren tube

Materials required:

  1. Westergren tube or wintrobe tube
  2. Anticoagulant: 0.1 M sodium citrate
  3. ** in modified westergren method EDTA is used as anticoagulant


Procedure for ESR estimation:

  1. Withdraw 4 ml of venous blood
  2. Mix exact 10ml of sodium citrate with 4ml of venous blood in a tube
  3. Invert the tube 2-3 times to mix the blood thoroughly with anticoagulant
  4. Fill the westergren tube up to mark 0 and place in the rack at room temperature undisturbed and away from sunlight.
  5. Take the reading exactly after 1 hour. Record in millimeters from top surface of column to top of RBC sediments.

Result:

  1. Normal value of ESR
    1. Female:
      1. under 50 years- 20 mm/hr
      2. above 50 years- 30mm/hr
    2. Male:
      1. Under 50 years- 15mm/hr
      2. Above 50 years- 20 mm/hr


Clinical application of ESR estimation:

  1. ESR test is non-specific test although it is used as indication of presence of disease
  2. ESR value increase during rheumatoid arthritis, chronic infection, carcinoma, tissue destruction and nephritis
  3. During pregnancy, ESR increase moderately from 10th or 12th weeks onwards and return to normal after delivery.
  4. ESR value decreases in sickle cell anemia and congestive heart failure (CHF).