Erythrocyte Sedimentation Rate (ESR): Significance, Stages, Methods, Interpretation and Reference Ranges
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The erythrocyte sedimentation rate (ESR) measures the rate of settling (sedimentation) of erythrocytes in anticoagulated whole blood. Anticoagulated blood is allowed to stand in a glass tube for 1 hour and the length of column of plasma above the red cells is measured in millimeters; this corresponds to ESR. There are four different methods for the estimation of ESR.
The Erythrocyte Sedimentation Rate (ESR) measures the rate of settlement of erythrocytes in anticoagulated blood. Anticoagulated blood is allowed to stand in a glass tube for an hour and the plasma above the red cells is measured in millimeters; this is called ESR.
STAGES OF ESR
- Stage 1: Lag pahse or rouleaux formation: The RBCs stack together and form a structure like package of coins in a shape of canned. (10 Minutes)
- Stage 2: Submerged of rouleaux. (40 Minutes)
- Stage 3: Slow sedimentation. (10 Minutes)
COMPONENTS INFLUENCING ON ERYTHROCYTE SEDIMENTATION RATE
- Red Blood Cells: In polycythemia, the mass of the red blood cells increases which cause the decrease of ESR. In Anemia the mass of the red cells decreases which cause the increase of ESR. In other words, Erythrocyte Sedimentation Rate is indirectly proportional to ratio between mass of the red cells and plasma.
- Plasma: The most important component influencing on Erythrocyte Sedimentation Rate is the composition of plasma. High level of C-Reactive Protein, fibrinogen, heptoglobin, a1-antitrypsin, ceruloplasmin and immunoglobulins causes the elevation of Erythrocyte Sedimentation Rate. When the level of proteins increases in plasma, it reduce the negative charge from the surface of red cells and depreciate the zeta potential; this facilitate the attraction between red blood cells, and form rouleaux.
- Technical Issues: Elevation in room temperature also affects the Erythrocyte Sedimentation Rate. Moving tube in sloping position, length and calibre of the tube also affect Erythrocyte Sedimentation Rate.
IMPORTANCE OF ERYTHROCYTE SEDIMENTATION RATE
Erythrocyte Sedimentation Rate is not a specific and diagnostic test for any particular disease. However, Erythrocyte Sedimentation Rate is elevated in a wide range of infectious diseases.
METHODS FOR ESTIMATION OF ERYTHROCYTE SEDIMENTATION RATE
There are four methods for the estimation of Erythrocyte Sedimentation Rate.
- Wintrobe method
- Westergren method
- Zeta Sedimentation Ratio
Wintrobe tube is used for both packed cell volume (PCV) and Erythrocyte Sedimentation Rate. Wintrobe’s method is more trustworthy when Erythrocyte Sedimentation Rate is low, while Westergren’s method is more impervious for elevated Erythrocyte Sedimentation Rate. Ethylenediaminetetraacetic acid (C10H16N2O8) is used as an anticoagulant. The internal diameter of Wintrobe tube is about 3 mm and the length is about 110 mm.
After getting the result of Erythrocyte Sedimentation Rate in the first hour, the tube can be whirl in a centrifuge to get the Packed Cell Volume (PCV).
Westergren ESR tube and Westergren stand.
The composition of Trisodium citrate dihydrate (C6H5Na3O7.2H2O or C6H9Na3O9) is as follows:
- Trisodium citrate dihydrate 32.08 gm
- Distilled water upto 1000 ml
After making this composition, the mixture is filtered through a sterile membrane (0.22 µm) and stored in a refrigerator at 4°C. The shelf life of this solution is of few months. When the solution becomes turbid (due to the growth of moulds), it should be disposed.
Venous blood is collected in trisodium citrate solution in 4:1 (blood:citrate) proportion. The test should be performed within 4 hours of blood collection.
- Mix the anticoagulated blood smaple thoroughly. Fill the Westergren tube with blood upto “ZERO” mark. Note that there is no air bubbles in the blood.
- Place the tube is vertical position in the ESR stand and left for an hour.
- Just exactly after an hour, read the height of the column of plasma above the red cells column in mm.
- Result is express in the following manner:
Erythrocyte Sedimentation Rate = ________ mm in an hour.
- Always use the correct ratio of anticoagulant and blood. Blood should be check for clots and air bubbles before going to the further process. Blood and anticoagulant should be mix thoroughly.
- Make sure that the temperature of the room is between 18-25°C. If the room temperature is elevated than 25°C, Erythrocyte Sedimentation Rate will increase and different reference range will acquire.
- ESR tube must be in strict vertical position. Even a slight tilting will cause elevation in Erythrocyte Sedimentation Rate.
Capillary blood is uses for the estimation of Micro-ESR. This method is recommended for the estimation of Erythrocyte Sedimentation Rate in small children.
ZETA SEDIMENTATION RATIO
In this method a special device is uses named zetafuge. Zeta Sedimentation Ratio is not pretended due to anemia, unlike Westergren method.
Erythrocyte Sedimentation Rate by Wintrobe Method
- Male 0-9 mm in an hour
- Female 0-20 mm in an hour
- Children 0-13 mm in an hour
Erythrocyte Sedimentation Rate by Westergren Method
- Males < 50 years 0-15 mm in an hour
- Females < 50 years 0-20 mm in an hour
- Children 0-10 mm in an hour
- Elderly males > 50 years 0-20 mm in an hour
- Elderly females > 50 years 0-33 mm in an hour