Centrifuge at 10,000 rpm for 5 minutes.
(7) Remove the hematocrit tubes as soon as the centrifuge has stopped
spinning. Determine the hematocrit values with the aid of a microhematocrit reader.
Results should agree within +2 percent. If they do not, repeat the procedure.
Since there are a variety of readers available, it is necessary that the
technician carefully follow the directions of the manufacturer for the particular
c. Sources of Error.
Inadequate mixing of the blood prior to sampling.
(2) Improper sealing of the capillary tube causes the blood to blow out of the
capillary tube during centrifugation.
(3) Capillary tubes must be properly identified. Numbered holders for
capillary tubes are available. Place the tubes in slots on the holder and record the
numbers on the laboratory request slip.
(4) Improper centrifugation leads to varied results. For good quality control,
maintain prescribed centrifuge speed and time.
Misreading the red cell level by including the buffy coat causes elevated
(1) The microhematocrit technique is advantageous because of speed, and
because only a small quantity of blood is necessary for the determination. An additional
advantage is the ease with which this procedure is adapted to infants and small
children. The microhematocrit technique requires only a simple capillary puncture
whereas in the Wintrobe method venous blood oust be used. Another advantage is the
use of disposable capillary tubes.
(2) If the microhematocrits cannot be read promptly, the capillary tubes
must be properly identified and placed in a vertical position. Slanting of the cell layer
will occur if tubes are left in a horizontal position for more than 30 minutes.
(3) Hematocrit results may also re obtained or computed through use of an
electronic cell counter (Coulter Models). Results of computed hematocrits are generally
1.3 to 3.0 percent higher due to their method of derivation. An accurate erythrocyte
count (three simultaneous electronic counts averaged) is multiplied by an accurate MCV