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Lesson 6-2. Erythrocyte Sedimentation Rate

ERYTHROCYTE SEDIMENTATION RATE

When anticoagulated whole blood is allowed to stand for a period of time, the red blood cells settle out from the plasma. The rate at which the red cells fall is known as the erythrocyte sedimentation rate (ESR). The ESR is affected mainly by three factors: erythrocytes, plasma, and mechanical and technical factors.

Erythrocytes. Size and shape of erythrocytes cause the ESR to fluctuate. Microcytes tend to settle slower than normal cells, while macrocytes fall more rapidly. An increase in spherocytes and/or bizarrely-shaped red cells retards the sedimentation rate. With a decreased hematocrit there is less retardation of sedimentation by the erythrocytes themselves and they tend to settle faster. Corrections for anemic blood are available; however, most experts consider this correction useless and invalid. An increased hematocrit (above 55 percent) retards the sedimentation rate.

Plasma Composition. In certain diseases plasma proteins, namely fibrinogen and globulin, may be altered, causing rouleaux formation. The speed of the sedimentation corresponds to the length of the rouleaux formation. Increases in fibrinogen or globulin will produce long rouleaux that are difficult to disperse. This leads to a larger mass and an increased sedimentation velocity.

Mechanical Technical Factors. It is important that the ESR tube be exactly perpendicular. A tilt of 30 can cause errors up to 30 percent. Vibration or movement of the ESR tube or holding rack can affect the ESR as can extreme changes in temperature.

Erythrocyte Sediment Rate. Determination of the ESR is performed by many methods of the more common methods; the Wintrobe-Landsberg and modified Westergen methods are stated in this lesson.

DETERMINATION OF SEDIMENTATION RATE (WINTROBE-LANDSBERG)

Anticoagulated blood is placed in a narrow tube. The blood cells settle out of the suspension, leaving clear plasma above them. The distance that the erythrocytes fall within a given interval of time is measured.

Procedure.

  1. Draw 5 ml of blood by venipuncture and place in a test tube containing ethylenediaminetetraacetic acid (EDTA) (lavender top vacuum tube).
  2. (Thoroughly mix the blood and anticoagulant by gently inverting the tube several times, being careful not to cause bubbles.
  3. Draw the blood into the capillary pipet and fill the Wintrobe tube to the 0 mark. This is done by inserting a capillary pipet to the bottom of the Wintrobe tube, while holding it at an angle of 45. As the tube is filled, slowly withdraw the pipet so that the tip is always just below the level of the blood. The blood count must be free of bubbles.
  4. Place the filled Wintrobe tube in a rack in an exactly vertical position and note the time and room temperature.
  5. At the end of exactly 1 hour, read the level to which the red cells have settled on the descending scale etched on the tube. Each mark equals 1.0 mm while each numbered mark equals 10 mm (1 cm). The figure obtained is reported in mm per hour as the "uncorrected" erythrocyte sedimentation rate.
  6. If a "corrected" sedimentation is requested, perform a hematocrit. Calculators to correct for sedimentation rate are available in the Federal Supply Catalog.

Sources of Error.

  • The blood specimen must be properly mixed with the proper anticoagulant to obtain an undiluted representative sample.
  • The test should be set up within two hours after the blood sample is collected to avoid a false low sedimentation rate.
  • Increase in temperature accelerates the rate. Desirable temperature range is 22 C to 27 C.
  • The tube must be vertical. A three-degree variation from the vertical rate accelerates the rate by 30 percent.
  • Dirty Wintrobe tubes or capillary pipets can decrease the rate.
  • Tubes should be placed free from vibration or disturbance.

Normal View.

  • Males: 0 to10 mm/hr.
  • Females: 0 to 15 mm/hr.
  • Children: 0 to 10 mm/hr.

 

DETERMINATION OF SEDIMENTATION RATE

Well-mixed, whole blood is diluted with 0.85 percent sodium chloride placed in a Westergren pipet, and allowed to stand for exactly one hour. The number of millimeters the red cells fall during this tie period constitutes the ESR result.

Procedure.

  1. Mix the whole blood and the anticoagulant by gently inverting the tube several times or by placing on a rotator for two minutes.
  2. Place 0.5 ml of 0.85 saline in a plain 13 X 100 mm test tube (usually commercially prepared and pre-measured).
  3. Add 2.0 ml of well-mixed whole blood to the test tube.
  4. Mix the tube for two minutes.
  5. Make certain that the Westergren ESR rack is exactly level.
  6. Fill the Westergren pipet to exactly the 0 mark, making certain there are no air bubbles in the blood.
  7. Place the pipet in the rack. Be certain the pipet fits snugly and evenly into the grooves provided for it.
  8. Allow the pipet to stand for exactly 60 minutes.
  9. At the end of 60 minutes, record the number of millimeters that the red cells have fallen. This result is the erythrocyte sedimentation rate in millimeters per hour.

Sources of Error.

  • The blood specimen must be properly mixed with the proper anticoagulant to obtain an undiluted representative sample.
  • The test should be set up within two hours after the blood sample is collected to avoid a false low sedimentation rate.
  • Increase in temperature accelerates the rate. Desirable temperature range is 22 C to 27 C.
  • The tube must be vertical. A three-degree variation from the vertical rate accelerates the rate by 30 percent.
  • Dirty Wintrobe tubes or capillary pipets can decrease the rate.
  • Tubes should be placed free from vibration or disturbance.
Normal Values.
  • Males: 0 to 10 mm/hr.
  • Females: 0 to 15mm/hr.
  • Children: 0 to10 mm/hr.

Discussion.

  • The erythrocyte sedimentation rate is a nonspecific test that suggests the possibility of a disease process and tissue damage in the body. It is not diagnostic but is extremely useful in following the course of some diseases.
  • The rate is usually increased in inflammatory infections, toxemia, cell or tissue destruction, severe anemia, active tuberculosis, syphilis, acute coronary thrombosis, rheumatoid arthritis, and malignant processes.
  • Sickle cell anemia, polycythemia, hypofibrinogenemia, and certain drugs usually decrease the rate.

 

 

David L. Heiserman, Editor

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Revised: June 06, 2015