- The rate at which the red blood cells or erythrocytes settle down is called ESR or erythrocyte sedimentation rate.
- In normal condition, red blood cells remain suspended uniformly in circulation which is called suspension stability of RBCs.
- Red blood cells settle down due to gravity with a supernatant layer of clear plasma when it is mixed with an anticoagulant and allowed to stand in a vertical tube.
- ESR is also known as sedimentation rate, sed rate or Biernacki reaction which was first demonstrated by Edmund Biernacki in 1897.
Determination of ESR
- ESR is determined by two methods as given below.
1) Westergren method
- This method is called so because Westergren tube is used here to determine ESR.
- This tube is open on both ends with the length of 300m and is marked 0 to 200 from above downwards.
- Here, blood is taken about 1.6ml and is mixed with 0.4 ml of 3.8% sodium citrate which acts as anticoagulant.
- This mixture is then loaded in Westregren tube where the ratio of blood to coagulant should be 4:1.
- The tube is then fitted vertically to the stand and left undisturbed which is then read at the end of one hour.
2) Wintrobe method
- In this method there is the use of Wintrobe tube to determine the ESR.
- The tube used here is a short tube which is opened on one end only and is of 110m length with 3mm bore.
- It is used not only for determining ESR but also to determine PCV.
- It is marked on both sides where one side is marked from 0 to 100 (for ESR) and the other side is marked from 100 to 0 (for PCV).
- Here anticoagulant used is EDTA which stands for ethylenediaminetetraacetic acid.
- This anticoagulant is mixed with one ml of blood and is loaded in the tube up to ‘0’ marks.
- After this, the tube is placed on Wintrobe stand and reading is taken after one hour.
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Normal values of ESR
A) By Westergren Method
In males: 3 to 7 mm in one hour
In females: 5 to 9 mm in one hour
Infants: 0 to 2 mm in 1 hour
B) By Wintrobe method
In males: 0 to 9 mm in one hour
In females: 0 to 15 mm in one hour
Infants: 0 to 5 mm in one hour
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Significance of ESR
- It is an easy, inexpensive as well as non-specific test that helps in diagnosis as well as prognosis.
- It cannot indicate the exact location or cause of disease so called non-specific tests though it helps in confirming the diagnosis.
- This test also helps in monitoring the course of disease and response of patient to therapy which we call prognosis.
- It is easy to assess the progress of patients treated for certain chronic inflammatory disorders such as pulmonary tuberculosis, rheumatoid arthritis, polymyalgia rheumatic which means inflammatory disease characterized by pain in shoulder and hip and temporal arteritis (inflammation of arteries of head).
Variations of ESR
1) Physiological variations
- In case of infants and children ESR is generally less.
- Because of less number of RBCs in females, ESR is more in females as compared to males.
- Due to loss of blood and RBCs during menstruation, ESR increases.
- ESR increases up to 35mm in 1 hour from 3d month to parturition because of hemodilution.
2) Pathological variation
- In diseases like tuberculosis, all types of anemia except sickle cell anemia, malignant tumors, rheumatoid arthritis, rheumatic fever and liver diseases, ESR increases.
- In allergic conditions, sickle cell anemia, peptone shock, polycythemia, severe leukocytosis, ESR generally decreases
Factors affecting ESR
- There are various factors that cause both increase and decrease in ESR. They are:
A)Factors increasing ESR
- Specific gravity of RBC: The cell becomes heavier if the specific gravity of RBC increases due to which sedimentation gets faster and ESR thus increases.
- Rouleaux formation: This also increases the ESR where globulin and fibrinogen accelerate the rouleaux formation.
- Increase in size of RBC: ESR increases with the increase in the size of the RBC (macrocyte).
B) Factors decreasing ESR
- Viscosity of Blood: Viscosity offers more resistance for settling of red blood cells due to which ESR decreases with the increase in the viscosity of the blood.
- RBC count: Increase in the count of RBC increases the viscosity of blood thus decreasing ESR whereas decrease in RBC count increases the ESR.
Erythrocyte Sedimentation Rate (ESR)