Elevated Neutrophil Count: Diagnostic Significance and Clinical Implications
An elevated neutrophil count (neutrophilia) primarily indicates an active infection, inflammatory process, or physiologic stress response, with bacterial infections being the most common cause requiring prompt evaluation and appropriate antimicrobial therapy. 1
Definition and Normal Values
- Normal neutrophil percentages in healthy adults typically range from 40-75% of total white blood cells 1
- Neutrophilia refers specifically to an elevated absolute neutrophil count, not just an increased percentage
- A "left shift" indicates an increased proportion of immature neutrophils (bands) in peripheral blood, suggesting active bone marrow response to infection 1, 2
Diagnostic Significance of Elevated Neutrophils
Strong Indicators of Bacterial Infection
- WBC >14,000 cells/mm³ (likelihood ratio 3.7)
- Band counts >1,500 cells/mm³ (likelihood ratio 14.5)
- Neutrophils >90% (likelihood ratio 7.5)
- Band neutrophils >16% (likelihood ratio 4.7) 1
Interpretation of Neutrophil Dynamics
- Elevated neutrophils with left shift indicates increased consumption matching increased production 2
- Decreasing WBC count with left shift suggests consumption exceeding production 2
- Time-series measurements are more valuable than single readings 2
Common Causes of Neutrophilia
Infectious Causes
- Bacterial infections (most common cause)
- Certain viral, fungal, and parasitic infections
- Localized infections (pneumonia, urinary tract infections, cellulitis)
- Systemic infections (sepsis)
Non-Infectious Causes
- Physiologic stress (surgery, trauma, burns, exercise)
- Inflammatory disorders (rheumatoid arthritis, vasculitis)
- Malignancies (especially hematologic)
- Medications (corticosteroids, lithium, epinephrine)
- Acute febrile neutrophilic dermatosis (Sweet's syndrome) 3
- Cardiovascular inflammation and myocardial infarction 4
- Metabolic disorders (diabetic ketoacidosis, uremia) 5
Clinical Evaluation of Neutrophilia
Initial Workup
- Complete blood count with differential (manual differential preferred for band count) 1
- Inflammatory markers (CRP, ESR, procalcitonin) to distinguish bacterial from non-bacterial causes 1
- Appropriate cultures based on clinical presentation:
Additional Testing Based on Clinical Context
- Imaging studies to identify source of infection
- Bone marrow evaluation for suspected hematologic disorders 1
- Neutrophil-to-lymphocyte ratio (NLR) - values >3.0 suggest inflammation/infection 1
Management Considerations
For Infectious Causes
- Culture appropriate specimens before starting antimicrobials
- Initiate empiric antimicrobial therapy based on likely pathogens
- Source control if needed (drainage of abscesses, removal of infected devices) 1
For Non-Infectious Causes
- Treat underlying condition
- Monitor trends in neutrophil counts rather than single measurements 1
- For severe neutrophilia (WBC >100 × 10⁹/L), consider:
- Intravenous hyperhydration
- Hydroxyurea or leukapheresis for symptoms of leukostasis 1
Clinical Pearls and Pitfalls
Pearls
- Neutrophil dynamics reflect the balance between bone marrow production and tissue consumption 2
- Neutrophils play important roles in both promoting inflammation and tissue healing 6
- The neutrophil-to-lymphocyte ratio can provide additional diagnostic information 1
Pitfalls
- Avoid attributing neutrophilia solely to stress without excluding infection 1
- Single time-point measurements may miss dynamic changes in neutrophil counts 2
- Neutrophilia may be absent in very early or late phases of infection 2
- Corticosteroid use can cause neutrophilia without infection