When reviewing results from a Complete Blood Count (CBC) with differential, the abbreviation “SEGS” often appears. SEGS is the shorthand used by laboratories for Segmented Neutrophils, which are the most abundant type of white blood cell circulating in the bloodstream. Analyzing the count of these cells provides medical professionals with insights into the body’s response to potential threats, particularly infection or inflammation.
What Segmented Neutrophils Are
Segmented neutrophils belong to leukocytes, or white blood cells. They are considered “segmented” because their nucleus is divided into multiple distinct lobes, typically ranging from two to five. This multi-lobed appearance distinguishes them from other white blood cells. Neutrophils are generated in the bone marrow, where they undergo maturation before being released into the peripheral blood. They are the most numerous type of white blood cell, making up approximately 40% to 60% of the total leukocyte count in a healthy adult.
The Primary Function of SEGS in Immunity
Segmented neutrophils act as the innate immune system’s rapid-response team, functioning as the first line of cellular defense against invading microorganisms. Their primary mission is to locate and neutralize pathogens, especially bacteria and certain fungi. They quickly migrate from the bloodstream to the site of injury or infection following chemical signals released by damaged tissues.
The main mechanism of defense employed by SEGS is called phagocytosis, which literally means “cell eating.” During this process, the neutrophil physically engulfs the invading bacterium, internalizing it within a vesicle. Powerful antimicrobial substances are then released into this vesicle, destroying the threat.
Understanding SEGS Results in a Blood Test
The segmented neutrophil count is reported as part of the differential white blood cell count, providing an absolute number and a percentage, both of which are measured against a laboratory’s established normal reference range. Deviations from this range carry clinical significance regarding the body’s current state of health.
A count higher than the upper limit is referred to as Neutrophilia. An elevated SEGS count frequently suggests an acute bacterial infection. The body responds to bacterial invasion by rapidly producing and releasing a large number of mature neutrophils to combat the threat. Neutrophilia can also occur in response to severe inflammation, physical stress, tissue damage from trauma or burns, or the use of certain medications like corticosteroids.
Conversely, a decreased SEGS count is known as Neutropenia, indicating a lower-than-normal number of mature circulating neutrophils. Neutropenia can arise from conditions that suppress bone marrow function, such as chemotherapy or certain blood disorders. It may also occur during overwhelming infections where neutrophils are consumed faster than the bone marrow can produce them. A low SEGS count compromises the body’s ability to fight off common bacterial infections, increasing the risk of severe illness.
The Significance of Immature Neutrophils (Bands)
The interpretation of the segmented neutrophil count is often paired with the observation of Band Neutrophils or “Bands.” Bands are neutrophils whose nucleus is shaped like a horseshoe or a thick curved rod, having not yet fully segmented. In a healthy person, bands are present in the blood in very low numbers, held in reserve by the bone marrow until they mature into SEGS.
A notable increase in circulating band neutrophils is referred to as a Left Shift. This signals that the bone marrow is under pressure to produce white blood cells so quickly that it is prematurely releasing immature cells into the bloodstream. A left shift is frequently associated with an acute bacterial infection, demonstrating the immune system’s urgent mobilization effort. Analyzing both SEGS and bands provides a complete picture of the immune response and the potential severity of an underlying condition.