Complete Blood Count (CBC)

The complete blood count (CBC) is a laboratory test that identifies the
number of red and white blood cells per cubic millimeter (mm3) of blood.
It is one of the most routinely performed blood tests and provides valuable
information about the patient's state of health. The CBC measures and evaluates
the cellular component of blood.
The tests included in the complete blood count are white blood cell
tests, which include the white blood cell count and the differential white
cell count; red blood cell tests, which include the red blood cell count,
hematocrit, and hemoglobin count; red blood cell indices, which include
the mean corpuscular volume, the mean corpuscular hemoglobin, and the
mean corpuscular hemoglobin concentration; and the thrombocyte test, or
platelet count.

HEMATOLOGY NORMAL RANGE
Hemoglobin 12-16 g/dl
Hematocrit 37-47%
Erythrocytes 4.2-5.4
Leukocytes 5000-10000/mm3
Neutrophils 55-70%
Monocytes 2-8%
Lymphocytes 20-40%
Basophils 0.5-1%
Eosinophils 1-4%
Platelet Count 140,000-400,000
MPV 2-4 m/diameter 

White Blood Cell Tests
The white blood cell count and the differential white blood cell count
identify the number and type of white blood cells present in the blood.
Both tests provide useful diagnostic information .
White Blood Cell Count; Leukocyte Count (WBC)
The white blood cell count identifies the number of white blood cells in a
specified volume of blood. The white cell count is then expressed as so
many thousand white blood cells per cubic millimeter (/mm3). Cell counting
is usually accomplished by an automated cell counter, but can be done
using a microscope with a special counting chamber.
Normal Range
Adults and Children 5000-10,000/mm 3
Children 2 years or younger 6200-17,000/mm 3
Newborns 9000-30,000/mm3
Variations from Normal. An increase in the overall number of white blood
cells is called leukocytosis . This is a very general term and can be the result
of a wide variety of conditions such as infection, hemorrhage, trauma, malignancy,
general hematologic problems, and leukemia. Adecrease in the
number of white blood cells is called leukopenia, andcan occur for reasons
that include viral infections, bone marrow disorders, spleen disorders, immune
problems, AIDS, and nutritional deficiencies .
Interfering Circumstances. The white cell count is affected by the time of
day (lower levels in the morning and a late afternoon peak), age, and gender.
Smoking can cause up to a 30% increase in total white blood cells.
Differential White Blood Cell Count; Differential Leukocyte Count (diff)
The differential white blood cell count is used to identify the percentage of
each type of white cell relative to the total number of leukocytes . The five
types of leukocytes are neutrophils, eosinophils, basophils, monocytes, and
lymphocytes. Each leukocyte has a unique function . Table 1-1 identifies
each type of white cell and its function.
Since each of the white cells is unique, normal range and clinical implications
of the increase or decrease in each type are presented individually .

Neutrophils
Neutrophils are the most numerous of the white cells and appear to be the
body's first defense against bacterial infection and severe stress . During an acute bacterial infection, neutrophils function as phagocytes. Neutrophils
remain in the blood stream for approximately 7-10 hours.
Neutrophils are also known as segmented neutrophils (segs) or polymorphonuclear
leukocytes (PMNs, polys). The names given to the neutrophils
depend on the maturity of the cells and the appearance of the
nucleus of the cells. Mature neutrophils are identified by their characteristic
segmented or lobed nucleus and are called segs, or segmented neutrophils.
Immature neutrophils are called bands or stabs because the nucleus
is not segmented.

Normal Range (Adult)
Neutrophils 55-70% of all white cells

Variations from Normal. An increase in the number of circulating neutrophils
is called neutrophilia and can be caused by various bacterial infections; inflammatory
diseases such as rheumatic fever, rheumatoid arthritis, stress, tissue
death or damage; and granulocytic leukemia. When reporting an increase
in neutrophils, the terms "shift to the left" or "shift to the right" may be used.
A shift to the left simply means that the increase in neutrophils is due to an increase
in the number of immature neutrophils. A shift to the right, although
rarely used, may indicate that abnormal or mature neutrophils predominate.
Adecrease in the number of circulating neutrophils is called neutropenia,
and can be caused by viral diseases and infections such as measles,
mumps, rubella, hepatitis, and influenza. Bone marrow injury and anorexia
nervosa can exhibit neutropenia.

Interfering Circumstances. Various treatments, such as radiation therapy and
chemotherapy, carry the risk of decreasing neutrophils. Antibiotics, psychotropic
medications, and some antidepressants can also play a role in neutropenia.
Lymphocytes (Lymphs)

Lymphocytes (lymphs) are an important part of the immune system and
play an active role in combating acute viral and chronic bacterial infections.
There are two types of lymphocytes, T cells and B cells. The differential
count does not identify or enumerate the number of T and B cells.

Normal Range (Adult)
Lymphocytes
20-40% of all white cells
Variations from Normal. An increase in the number of lymphocytes is called
lymphocytosis and is seen in a variety of diseases. Viral diseases such as
rubella, measles, mumps, viral respiratory infections, atypical pneumonia,
infectious hepatitis, and infectious mononucleosis exhibit lymphocytosis .
Bacterial infections such as syphilis and pertussis can also cause lymphocytosis.
Malignant causes of lymphocytosis are lymphocytic leukemia and lymphoma.
A decrease in lymphocytes is called lymphocytopenia and is seen primarily
when the immune system is suppressed as in diseases such as AIDS
and systemic lupus erythematosus.

Monocytes (Monos)
Monocytes (monos), although small in number, perform an important defense
function in the body. These large cells are phagocytes and respond to
bacteria in the same manner as neutrophils. Monocytes remain in circulation
longer than neutrophils and phagocytize bacterial and cellular debris.
Phagocytosis is the process of engulfing and destroying microorganisms
and cellular debris. Monocytes also act as phagocytes in some chronic inflammatory
diseases such as arthritis.

Normal Range
Monocytes
2-8% of all white cells

Variations from Normal. An increase in the number of monocytes is called
monocytosis and is seen during infections such as tuberculosis and bacterial
endocarditis. Diseases such as chronic ulcerative colitis, malaria,
rheumatoid arthritis, and hemolytic anemia can exhibit an increase in the
monocyte count. A decreased monocyte count is not usually identified
with any specific disease processes.
Eosinophils and Basophils (Eosinos, Basos)
Eosinophils (eosinos) are minimally phagocytic, but play a role in the antigen-
antibody response, in allergic reactions, in combating parasitic infections,
and in the dissolution of blood clots. The main function of eosinophils
seems to be to prevent the excessive spread of inflammation. Basophils
(basos) play an important role in allergic reactions by releasing the histamine
that is responsible for allergy symptoms.

Normal Range
Eosinophils 1-4% of all white cells
Basophils 0.5-1% of all white cells

Variations from Normal. An increase in eosinophils is called eosinophilia
and is associated with allergy attacks, asthma, hay fever, and parasitic infections.
Certain skin diseases, tuberculosis, Hodgkin's disease, and granulocytic
leukemia result in an increase in eosinophils. Adecrease in eosinophils
is called eosinopenia and is associated with an increase in adrenal steroid
production and acute bacterial or viral inflammation .
An increase in basophils is called basophilia, and is seen in myeloproliferative
diseases such as polycythemia vera and chronic granulocytic
leukemia. Chicken pox, small pox, chronic sinusitis, and ulcerative colitis
may also be present with basophilia. Because the normal basophil count is
small to begin with, a decrease in number may not be detected . However,
prolonged steroid therapy, hormone imbalance, thyrotoxicosis, and severe
allergic reactions often result in a basophil decrease.
Interfering Circumstances. As with other white blood cell counts, age, stress,
time of day, and steroid therapy can interfere with eosinophil and basophil
counts.