Neutrophils

Synonyms: segmented neutrophils, segs, polymorphonuclear leukocytes, polys, PMNs

What are Neutrophils?

Interpret now "Comprehensive Metabolic Panel (CMP)"
Interpret now "Urinalysis (UA)"

Neutrophils are the largest group of white blood cells that protect the body from various infections caused by bacteria or fungi and, to a lesser extent, by viruses. They make up 55 to 70% of the total volume of the white blood cells (leukocytes) in the bloodstream. Such a high level of neutrophils in the blood is necessary to protect the body against infectious agents. Neutrophils are formed in the bone marrow from stem cells.

Depending on the stages of neutrophils maturation, there are several neutrophil types:

• myeloblast
• promyelocyte,
• myelocyte
• metamyelocyte
• band neutrophil (bands)
• polymorphonuclear cell (segmented)

Segmented neutrophils have a segmented nucleus and are mature cells. The rest of the neutrophils are young (immature) cells. Segmented neutrophils outnumber the immature forms in the blood. In response to an infection or inflammatory process in the body, immature neutrophils are released into the blood by the bone marrow, and their amount may help detect a bacterial infection and its severity.

What is the Function of Neutrophils?

Neutrophils help the body fight against pathogen infections. There is a direct or indirect effect on pathogens:

• Phagocytosis. Neutrophils enter the tissues from the blood circulation and destroy alien pathogens through phagocytosis, that is, by absorbing and digesting foreign particles, and then die.
• Degranulation. The cytoplasm of neutrophils contains numerous granules. These granules contain microbicidal agents and help combat infection.

In case of inflammatory process in the body, neutrophils quickly find it and move to the foci of infection. Neutrophils are essential for resistance to bacterial infections. The stronger the bacterial inflammation, the more neutrophils are determined in leukocyte (WBC) count.

The appearance of immature neutrophils in the blood is called neutrophil left shift. When the number of mature segmented neutrophils increases (reduced count or lack of "young neutrophils") that is a shift of neutrophils to the right.

Neutrophil Count in Pregnancy

Physiological changes that occur during pregnancy affect virtually every organ system in the body. These changes are necessary for the proper growth and development of the child.

The total white blood cell count is frequently elevated in pregnancy due to high numbers of neutrophils. The transportation of neutrophils from the bloodstream to the tissues decreases, thereby increasing their concentration in the blood. Increased number of band neutrophils may be found in the blood; however, this neutrophilia is not usually associated with infection or inflammation.

Neutrophil Count in Children

A high neutrophil count is usually seen in neonates, but it is decreased in the first few days of life. The number of neutrophils is approximately equal to the number of lymphocytes by the age of 5. Then neutrophil count begins to rise and reaches an adult level by the age of puberty.

Neutrophil Count Units

The number of neutrophils in the blood can be expressed as a percentage (relative content) or in absolute numbers (total number of cells in a unit of blood).

The absolute number of neutrophils can be expressed in the following units:

SI units (International System of Units): 10⁹ cells/L, G/L (Giga per liter)

Conventional units: 10³/μL (1000/μL), 10³/mm³ (1000/mm³), K/μL (thousand cells per microliter (mcL)), K/mm³, cells/μL, cells/mm³.

The relative ratio is expressed as a percentage (%).

The conversion factor of different units:

10⁹ cells/L = G/L = 10³/μL (1000/μL) = 10³/mm³ (1000/mm³) = K/μL = K/mm³cells/μL (cells/mm³) = 1000 * K/μL (K/mm³)

What is the normal range for neutrophils?

The absolute neutrophil count (ANC) can be calculated as:

ANC = NEU x WBC / 100

where:

NEU - total neutrophil count (%)

WBC - white blood cells (10⁹ cells/L)

Reference values for neutrophils may vary between laboratories. For most laboratories, the normal range for neutrophils count in adults is as follows:

• segmented neutrophils: 40-70% or 1700-7200 cells/μL (1.7-7.2 x10⁹ cells/L)
• band neutrophils: 1-6% or 100-600 cells/μL (0.1-0.6 x10⁹ cells/L)

What is the normal range for neutrophils in pregnancy?

The number of neutrophils increases during pregnancy. An increase in the neutrophil count to 13,000 cells/μL (13 x10⁹ cells/L) or up to 80% is considered normal during pregnancy.

What is the normal range for neutrophils in children?

Neutrophil reference values for children differ from adult values and vary by age. A small number of immature forms can be found in children.

The number of neutrophils is increased at birth. Then the level of neutrophils gradually decreases and reaches an adult level in adolescence.

High Neutrophil Counts (Neutrophilia)

Neutrophilia, an increased number of neutrophils, is the body’s defense mechanism against infections and inflammations. Neutrophilia is generally present along with leukocytosis and is more typical for bacterial infections. Neutrophil levels can also increase in response to emotional or physical stress.

The higher the number of neutrophils, the more severe the disease. A left shift indicates the presence of immature neutrophils in the blood. It is quite typical for bacterial infections but can accompany any inflammatory process.

What can cause high neutrophils?

Neutrophilia can be caused by different conditions, such as:

• infections, most likely bacterial
• acute and severe chronic inflammation (inflammatory bowel disease, rheumatoid arthritis, ulcerative colitis, gout)
• some viral (eg, chickenpox, herpes simplex), fungal, and parasitic infections
• excessive exercise
• high stress
• recent vaccination;
• drugs, especially corticosteroids
• necrosis
• injury or surgery
• cytotoxic chemotherapy
• heart attacks

High Neutrophils in Pregnancy

Physiological changes that occur during normal pregnancy can cause changes in laboratory parameters that are considered abnormal in non-pregnant women. During pregnancy, the level of neutrophils may be slightly increased. According to some reports, neutrophils can increase to:

• 10.1 x10³/mm³ (10,100 cells/mcL) in the first trimester
• 12.3 x10³/mm³ (12,300 cells/mcL) in the second trimester
• 13.1 x10³/mm³ (13,100 cells/mcL) in the third trimester

High Neutrophils in Child

A slight increase in neutrophil levels in children is not always a cause for concern. It can be seen after physical activity, stress, overheating, excessive crying. You should see a doctor if there is a constant and/or significant increase in the neutrophil count.

Low Neutrophil Counts (Neutrophilia)

Neutrophils play an important role in protecting the body against various infections. A low number of neutrophils increases susceptibility to infections.

Neutropenia, a decrease in the number of neutrophils, indicates a functional or organic suppression of blood formation in the bone marrow or increased destruction of neutrophils. Neutropenia is generally an indicator of a weakened immune system.

Agranulocytosis is a decrease in the number of neutrophils less than 500 per microliter of blood (0.5 x10⁹ cells/l).

Regardless of the causes, neutropenia can be divided into two main categories:

1. Neutrophils are destroyed faster than the bone marrow produces new ones.
2. The production of neutrophils in the bone marrow is reduced.

Neutropenia is classified according to severity as:

• mild – from 1000-1500 cells/μL (1 to 1.5 x10⁹ cells/L)
• moderate – from 500-1000 cells/μL (0.5 to 1 x10⁹ cells/L)
• severe – less than 500 cells/μL (0.5 x10⁹ cells/L)

Neutropenia is generally an indicator of a weakened immune system. In most cases, neutropenia is caused by a recent illness, infection, or medication. The neutrophils return to normal levels within 3-6 weeks.

Other causes of low neutrophils are:

• diseases that affect the bone marrow (aplastic anemia, cancer)
• vitamin B-12 deficiency
• hepatitis, HIV/AIDS
• chemotherapy
• autoimmune disorders (rheumatoid arthritis)

Low Neutrophils in Pregnancy

A low number of neutrophils is not normal in pregnancy. The possible causes of neutropenia are the same as for non-pregnant women.

Low Neutrophils in Children

The normal range for neutrophils in children differs from those in adults. In children under 1 year old, the lower limit of the neutrophil count is 1000 cells/μL (1 x10⁹ cell/L). In older children, the lower limit of neutrophils is 1500 cells/μL (1.5 x10⁹ cells/L).

4% of the world's population has benign ethnic neutropenia (BEN; aka constitutional neutropenia). This condition is not usually associated with an increased risk of infections. It is an inherited disorder that causes mild or moderate neutropenia.