What is the management for a patient with leukocytosis (elevated white blood cell count) and a neutrophilic shift, suggesting a potential bacterial infection?

Management of Leukocytosis with Neutrophilic Shift

Leukocytosis with a neutrophilic shift strongly suggests bacterial infection and requires prompt initiation of appropriate empiric antibiotic therapy after obtaining relevant cultures, followed by targeted therapy once the pathogen is identified. 1

Initial Assessment

When evaluating a patient with leukocytosis and neutrophilic shift, consider:

• Severity indicators:

  • WBC count >14,000 cells/mm³ (LR 3.7 for bacterial infection)
  • Band neutrophils >16% (LR 4.7 for bacterial infection)
  • Band neutrophil count >1,500 cells/mm³ (LR 14.5 for bacterial infection)
  • Neutrophils >90% (LR 7.5 for bacterial infection) 1

• Clinical context:

  • Presence of fever
  • Focal signs of infection
  • Patient's immune status
  • Recent antibiotic exposure
  • Healthcare vs. community setting

Diagnostic Workup

1. Complete blood count with manual differential to assess:

   • Total WBC count
   • Percentage and absolute count of band neutrophils
   • Presence of toxic granulations 2, 1

2. Culture specimens before initiating antibiotics:

   • Blood cultures (2 sets)
   • Urine culture if urinary symptoms present
   • Sputum culture if respiratory symptoms present
   • Other cultures as clinically indicated 2

3. Imaging studies based on suspected source:

   • Chest radiography for respiratory symptoms
   • CT scan for suspected intra-abdominal infection 2

Treatment Algorithm

For Immunocompetent Patients:

1. Identify likely source of infection

2. Initiate empiric antibiotics based on suspected source:

   • Community-acquired pneumonia: Respiratory fluoroquinolone or β-lactam plus macrolide
   • Urinary tract infection: Fluoroquinolone or 3rd generation cephalosporin
   • Intra-abdominal infection: β-lactam/β-lactamase inhibitor or 3rd generation cephalosporin plus metronidazole
   • Skin/soft tissue infection: Anti-staphylococcal penicillin or 1st generation cephalosporin

3. Adjust therapy based on culture results and clinical response within 48-72 hours

For Neutropenic Patients:

1. Immediate broad-spectrum antibiotics after cultures:

   • Monotherapy with anti-pseudomonal β-lactam (cefepime 2g IV every 8 hours) 3
   • Consider adding vancomycin if MRSA suspected or line infection present 2

2. Reassess at 48 hours:

   • If afebrile and ANC ≥0.5×10⁹/L: Consider oral antibiotics if low-risk
   • If still febrile but clinically stable: Continue initial therapy
   • If clinically unstable: Broaden coverage or rotate antibiotics 2

3. Duration of therapy:

   • If neutrophil count ≥0.5×10⁹/L, afebrile for 48 hours, and negative cultures: Discontinue antibiotics
   • If neutrophil count <0.5×10⁹/L but afebrile for 5-7 days without complications: Consider discontinuing antibiotics
   • If persistent fever >4-6 days: Consider antifungal therapy 2

Special Considerations

Non-infectious Causes of Leukocytosis with Left Shift

• Physiologic stress: Surgery, trauma, burns, exercise
• Medications: Corticosteroids, lithium, epinephrine
• Inflammatory conditions: Rheumatoid arthritis, inflammatory bowel disease
• Malignancy: Leukemia, lymphoma 4

Pitfalls to Avoid

1. Relying on a single WBC measurement rather than monitoring trends
2. Attributing normal WBC to absence of infection (present in only 25% of cases)
3. Failing to consider non-infectious causes of leukocytosis
4. Delaying antibiotics in neutropenic patients with fever 1

Monitoring

• Serial CBC monitoring to assess response to therapy
• Daily assessment of fever trends and clinical status
• Monitor for complications such as organ dysfunction or sepsis 2, 1

Remember that the neutrophilic response is dynamic during infection, with changes in both WBC count and left shift reflecting the progression from onset to recovery. A decrease in WBC count with persistent left shift may indicate that neutrophil consumption is exceeding bone marrow production, suggesting worsening infection 5.