Step 17: Erythrocyte Sedimentation Rate

Erythrocyte sedimentation rate (ESR) is the measurement of the rate that RBCs will settle toward the bottom of a vertical tube if the sample is well mixed and the blood is anticoagulated. The ESR is used for diagnosis and treatment of diseases because it is easy to perform, accurate and fairly inexpensive. The ESR is often referred to as the sed rate.

When the body has a disease, the plasma protein (fibrinogen) will be altered which will affect the sedimentation rate. Similarly, the surface of the RBC can be altered by disease and will affect the sedimentation rate.

The sed rate is taken in two ways, by using either the Wintrobe method or the Westergren method.

Wintrobe Method

In order to conduct an ESR test using the Wintrobe method, a venous blood sample is mixed well with an anticoagulant and transferred to a Wintrobe tube. A Wintrobe tube is a thick-walled glass tube with a flat bottom and millimeter marks from 0 to 105.4.

This example of a Wintrobe tube shows a sedimentation of 12 mm.

The blood is filled to the zero at the top of the tube and there should be no air bubbles. The tube sits vertically in a rack for 60 minutes to allow the red blood cells and plasma to separate. The sed rate is the number of millimeters that the red blood cells have fallen from the zero mark. A normal value for males is 0 to 9 millimeters per hour (mm/hr), while a normal value for females is 0 to 20 mm/hr.

Westergren Method

The Westergren method is similar to the Wintrobe method with the exception of the reagent used—the Westergren test calls for a 3.8 percent sodium citrate solution well mixed in the sample before transferring it to the tube.

The normal values for Westergren method results are as follows:

• Male patients older than 50 years should be between 0 and 20 mm/hr
• Male patients younger than 50 years should be between 0 and 15 mm/hr
• Female patients older than 50 years should be between 0 and 30 mm/hr
• Female patients younger than 50 years should be between 0 and 20 mm/hr

If the results are higher than normal in either the Westergren or Wintrobe methods, it could mean the patient has an infection, inflammatory disease or tissue destruction. Menstruation, pregnancy, myeloma and anemia can also cause a higher sed rate. Decreased values can be the result of conditions such as sickle cell anemia, spherocytosis and polycythemia. ESR may read normal in patients with conditions such as osteoarthritis, cirrhosis and malaria.

 

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