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newborns the range is from 10,000 to 30,000 cells per
cubic millimeter.
White blood cell counts are performed either
manually or with automated hematology analyzers.
Only the manual method will be covered in this
chapter. After a brief discussion on abnormal white
blood cell counts, we will cover the Unopette method
for manually counting white blood cells.
Abnormal White Cell Counts
When white cell counts rise above normal values,
the condition is referred to as leukocytosis.
Leukocytosis frequently occurs when systemic or
local infections (usually due to bacteria) are present.
Counts for infections are highly variable. Examples of
some infections and their representative white cell
counts are as follows:
Pneumonia—20,000 to 30,000/mm3
Meningitis—20,000 to 30,000/mm3
Appendicitis—10,000 to 30,000/mm3
D y s c r a s i a
( t h e d i s e a s e d c o n d i t i o n ) o f
blood-forming tissues, such as occurs in leukemia (due
to a malfunctioning of lymph and marrow tissues) also
results in leukocytosis, with extremely high white cell
counts. These white cell counts sometimes exceed
1,000,000/mm3.
Other physiological conditions that can cause
leukocytosis and a white cell count as high as
15,000/mm3 may occur as follows:
· Shortly after birth
· During late pregnancy
· During labor
· Accompanying severe pain
· After exercise or meals
· After cold baths
· During severe emotional upset
An abnormally low count, known as leukopenia,
may be caused by the following conditions:
· Severe or advanced bacterial infections (such as
typhoid, paratyphoid, and sometimes
tularemia), or when the bacterial infection has
been undetected for a period of time (as with
chronic beta streptococcal infections of the
throat).
· Infections caused by viruses and rickettsiae,
such as measles, rubella, smallpox (until the 4th
day), infectious hepatitis, psittacosis, dengue,
tsutsugamushi fever, and influenza (when it may
fall to 1,500/mm3, or shift to leukocytosis if
complications develop).
· Protozoal infections (such as malaria) and
helminthic infections (such as trichinosis). (For
example, with victims of malaria, slight
leukocytosis may develop for a short time during
paroxysm (the sudden intensification of
symptoms).
Shortly thereafter, however,
leukopenia ensues.)
· Overwhelming infections when the body’s
defense mechanisms break down.
· Anaphylactic shock
· Radiation
Materials Required for Unopette Procedure
The Unopette method uses a disposable diluting
pipette system that provides a convenient, precise, and
accurate method for obtaining a white blood cell count.
When the Unopette method is used, whole blood is
added to a diluent. The diluent lyses (destroys) the red
blood cells, but preserves the white blood cells. Once
the red cells are completely lysed, the solution will be
clear.
The diluted blood is then added to a
hemacytometer. Once the hemacytometer is loaded,
the cells should be allowed to settle for 10 minutes
before counting proceeds.
The following materials are required to perform a
white blood cell count using the Unopette method:
· Disposable Unopette for WBC counts, which
consists of
—a shielded capillary pipette (20 microliter (Fl)
capacity), and
—a plastic reservoir containing a premeasured
volume of diluent (1:100 dilution).
· Hemacytometer and coverglass
· Microscope with light source
· Hand-held counter
· Laboratory chit
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