From the Guidelines
An increase in neutrophils is indicated by a high percentage of neutrophils (>90%) and band neutrophils (16%, i.e., “left shift”) in the blood, as well as an elevated total band count (>1500/mm3) 1.
Indicators of Neutrophil Increase
Neutrophils increase in response to various stimuli, including:
- Bacterial infections, such as pneumonia, urinary tract infections, and skin infections
- Inflammatory conditions, like rheumatoid arthritis and inflammatory bowel disease
- Physical or emotional stress
- Tissue damage from burns, heart attacks, or surgery
- Certain medications, such as corticosteroids and epinephrine
Diagnostic Criteria
Blood tests showing neutrophil counts above 7,500 cells per microliter (or above 70% of total white blood cells) can confirm neutrophilia 1.
Clinical Presentation
Symptoms that might accompany increased neutrophils include:
- Fever
- Fatigue
- Pain
- Swelling
- Redness at infection sites The increase in neutrophils occurs because the bone marrow releases more neutrophils into circulation when the body detects pathogens or inflammation, as neutrophils are the first line of defense against bacterial infections 1.
Pathophysiology
They migrate to infection sites, engulf bacteria, and release enzymes to destroy pathogens, playing a crucial role in the immune response.
Key Findings
A study published in the Clinical Infectious Diseases journal found that an elevated total band count (>1500/mm3) had the highest likelihood ratio (14.5) for detecting documented bacterial infection 1.
Clinical Implications
In clinical practice, an increase in neutrophils can be a useful indicator of underlying bacterial infection, particularly in older adults 1.
From the Research
Indicators of Increased Neutrophils
- A band count greater than 10% is often used as a clinical indicator of sepsis, as stated in the study 2
- The presence of immature neutrophils (bands) in the circulating blood can be a useful indicator of infection, with a sensitivity of 43% and specificity of 92% for the diagnosis of infection 2
- An elevated white blood cell (WBC) count, particularly a WBC count greater than 12 × 10(9)/L, may also be an indicator of infection, although its diagnostic accuracy is limited 2
Neutrophil Response to Infection
- Neutrophils play a crucial role in host defense against infection, and their dysfunction can lead to poor outcomes, as seen in older adults and preterm infants 3
- Neutrophils are among the first responders to infection, and their ability to target infected or inflamed tissue, phagocytose pathogens, and release neutrophil extracellular traps (NETs) is essential for effective host defense 3, 4, 5
- The reversal or restoration of neutrophil function can promote bacterial clearance and improve sepsis outcome, supporting the idea that targeting neutrophils may be a promising strategy for sepsis treatment 4
Diagnostic Methods
- Raman spectroscopy can be used to characterize neutrophils and detect infections, including bacterial and fungal infections, with high accuracy 6
- This method enables reliable neutrophil phenotyping and infection diagnosis in a label-free manner, potentially saving precious time in bloodstream infection diagnostics 6