Neutrophilia: Definition, Causes, and Clinical Significance
Neutrophilia is defined as an elevated neutrophil count above 1500 cells/mm³ in the peripheral blood, representing an abnormal increase in circulating neutrophils that often indicates an underlying inflammatory process, infection, or other pathological condition.
Definition and Classification
- Neutrophilia occurs when the absolute neutrophil count exceeds 1500 cells/mm³ in peripheral blood 1
- It represents the opposite condition of neutropenia, which is defined as a neutrophil count below 500 cells/mm³ or below 1000 cells/mm³ with a predicted decline to ≤500 cells/mm³ over the next 48 hours 2
- Normal neutrophil-to-lymphocyte ratio (NLR) is between 1-2, with values higher than 3.0 considered pathological and potentially indicative of inflammation or other disorders 3
Causes of Neutrophilia
Infectious Causes
- Bacterial infections are a primary cause of neutrophilia, with the body increasing neutrophil production in response to pathogens 2
- Severe infections and sepsis can cause dramatic increases in NLR values above 11, sometimes exceeding 30 3
- Common sites of infection leading to neutrophilia include the respiratory tract, skin/soft tissues, gastrointestinal tract, and genitourinary system 2
Non-Infectious Causes
- Cancer and malignancies, particularly solid tumors, often present with neutrophilia as part of cancer-related inflammation 3, 4
- Inflammatory conditions and autoimmune disorders trigger neutrophil mobilization 5
- Medications and treatments, including corticosteroids and certain chemotherapeutic agents 2
- Physiological stress, including surgery, trauma, and burns 3
- Neutrophilic dermatoses (Sweet syndrome, pyoderma gangrenosum, subcorneal pustular dermatosis) are characterized by inflammatory infiltrates of mature neutrophils 6
Clinical Significance
Diagnostic Value
- Neutrophilia serves as an early warning sign of infection, inflammation, or other pathological processes 3
- The neutrophil-to-lymphocyte ratio (NLR) is a sensitive indicator of systemic inflammation and stress 3
- Values in the "grey zone" between 2.3-3.0 may serve as early warning of pathological states such as cancer, atherosclerosis, infection, or inflammation 3
Prognostic Value
- In cancer patients, NLR correlates with tumor size, stage, metastatic potential, and lymphatic invasion 3
- NLR has independent prognostic value regarding overall survival and disease progression 3
- In infectious diseases, the severity of critical illness and level of stress is reflected by increasing NLR values 3
- Improvement in clinical course of sepsis and critical illness is associated with decline of NLR values below 7 3
Clinical Evaluation and Monitoring
- Neutrophilia should prompt investigation for underlying causes, particularly infections 2
- In patients with cancer receiving myelosuppressive chemotherapy, neutrophil counts should be monitored regularly to assess risk of infection 2
- Daily monitoring of NLR is recommended in acute disease or critical illness to track disease progression and response to treatment 3
- Dynamic changes in NLR may precede clinical deterioration by several hours, serving as an early warning system 3
Management Implications
- Recognition of neutrophilia helps guide appropriate antimicrobial therapy in suspected infections 2
- In cancer patients, neutrophilia may influence decisions regarding prophylactic use of colony-stimulating factors to prevent febrile neutropenia 2
- Understanding the cause of neutrophilia is essential for targeted treatment of the underlying condition 2
Neutrophilia represents an important clinical finding that should prompt further investigation to identify and address the underlying cause, particularly when associated with signs and symptoms of infection or inflammation.