From the Guidelines
Segmented neutrophils, or "segs" on a manual differential count, are mature neutrophils that have a segmented or multi-lobed nucleus connected by thin filaments. They are the most abundant type of white blood cell in normal blood, typically comprising 40-60% of the total white blood cell count in adults. Segs are part of the innate immune system and function as the body's first line of defense against bacterial infections by phagocytizing (engulfing and destroying) pathogens. During a manual differential count, laboratory technicians examine a blood smear under a microscope and identify different types of white blood cells based on their appearance, including the characteristic segmented nucleus of mature neutrophils. An elevated seg count (neutrophilia) often indicates bacterial infection, inflammation, or physiological stress, while a decreased count (neutropenia) may suggest viral infections, certain medications, or bone marrow disorders, as seen in some cases of agranulocytosis associated with medications like clozapine 1. The distinction between segs and bands (immature neutrophils) is important clinically, as an increase in band neutrophils ("left shift") typically suggests an active inflammatory response to infection. Key points to consider when evaluating segs on a manual differential count include:
- The normal range for segs in adults is typically between 40-60% of the total white blood cell count
- An elevated seg count may indicate bacterial infection, inflammation, or physiological stress
- A decreased seg count may suggest viral infections, certain medications, or bone marrow disorders
- The distinction between segs and bands is important clinically, as it can indicate the presence of an active inflammatory response to infection. In the context of primary immunodeficiency, the diagnosis of phagocyte defects, such as severe congenital neutropenia or chronic granulomatous disease, may involve the evaluation of segs on a manual differential count, as well as other laboratory tests and clinical features 1.
From the Research
Definition of Segs
- Segs, also known as segmented neutrophils, are a type of white blood cell that plays a crucial role in the immune system 2.
- They are characterized by a multilobed nucleus, typically with three to five lobes, and are an essential component of the white blood cell differential count.
Role in Manual Differential Count
- The manual differential count of white blood cells, including segs, is a labor-intensive process that requires skilled technicians to accurately identify and count different cell types 3, 4.
- The count of segs, along with other white blood cell types, provides valuable information for diagnosing various diseases and monitoring patient response to treatment 5.
Challenges in Classification
- The classification of neutrophils into segs and band neutrophils can be challenging due to the lack of unique quantitative definitions and the overlap of nuclei, which can lead to classification errors 2.
- Studies have shown that the accuracy of classification can be improved by using automated systems, such as dual-stage convolutional neural networks, which can classify white blood cells with high accuracy and precision 3.
Clinical Significance
- The count of segs, along with other white blood cell types, can provide valuable diagnostic information, particularly in critically ill patients, where an elevated band count may indicate infection 6.
- However, the diagnostic accuracy of an elevated band count for infection is limited, and should be used in conjunction with other clinical indicators and laboratory tests to confirm diagnosis.