measurement resulting in the area that the red cells would occupy if packed. The
computation makes no allowance for the trapped plasma that always occurs to sate
degree in manual packing procedures.
e. Normal Values.
Birth: 5062 percent.
Age 1: 31--39 percent.
Adult males: 4252 percent.
Adult females: 3646 percent.
Section II. ERYGHROCYTE SEDIMENTATION RATE
ERYTHROCYTE SEDIMENTATION RATE
a. Introduction. When anticoagulated whole blood is allowed to stand for a
period of time, the red blood cells settle out frail 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.
b. 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.
c. 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.
d. 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 large changes in temperature.
e. ERYTHROCYTE SEDIMENTATION 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.