How should a patient with leukocytosis and neutrophilia be managed, considering the possibility of a bacterial infection?

Management of Leukocytosis with Neutrophilia

A WBC of 13.2 × 10⁹/L with 89.3% neutrophils indicates likely bacterial infection and requires immediate clinical assessment for infection source, followed by targeted diagnostic workup including manual differential to assess for left shift, with empiric antibiotics initiated only if sepsis criteria are met or a specific infection source is identified. 1, 2

Immediate Diagnostic Priority

Your patient has moderate leukocytosis (13.2 × 10⁹/L) with marked neutrophilia (89.3%), which carries significant diagnostic weight for bacterial infection:

• WBC ≥14,000 cells/mm³ has a likelihood ratio of 3.7 for bacterial infection, even without fever 1, 2
• Neutrophil percentage >90% has a likelihood ratio of 7.5 for bacterial infection 1—your patient at 89.3% approaches this threshold
• The combination of elevated WBC and high neutrophil percentage warrants careful assessment for bacterial infection regardless of fever presence 3, 1

Essential Next Steps Within 12-24 Hours

1. Obtain Manual Differential Count (Critical)

• Manual differential is mandatory—automated analyzers miss band forms and immature neutrophils 3, 2, 4
• Calculate absolute band count: if ≥1,500 cells/mm³, this has the highest likelihood ratio (14.5) for documented bacterial infection 1, 2, 4
• Assess for left shift (≥16% band neutrophils): has likelihood ratio of 4.7 for bacterial infection, even with normal total WBC 1, 4
• This must be done within 12-24 hours of suspected infection onset 3

2. Systematic Clinical Assessment for Infection Source

Evaluate for these specific findings:

Respiratory tract 2, 4:

• Cough, dyspnea, chest pain, hypoxemia
• If present: pulse oximetry and chest radiography

Urinary tract 3, 2, 4:

• Dysuria, flank pain, frequency, new or worsening incontinence
• If present: urinalysis for leukocyte esterase/nitrite and microscopic WBCs
• Do NOT obtain urine culture in asymptomatic patients 3

Skin/soft tissue 2, 4:

• Erythema, warmth, purulent drainage, cellulitis

Gastrointestinal 2, 4:

• Abdominal pain, peritoneal signs, diarrhea
• Consider intra-abdominal infection or C. difficile if colitis symptoms present

Systemic signs of sepsis 2:

• Fever >38°C or hypothermia <36°C
• Hypotension <90 mmHg systolic
• Tachycardia, tachypnea
• Altered mental status
• If lactate >3 mmol/L: indicates severe sepsis requiring immediate intervention 2

3. Targeted Laboratory and Imaging

Blood cultures 2, 4:

• Obtain if any signs of systemic infection (fever, hypotension, tachycardia, altered mental status)
• Do NOT routinely obtain in stable, asymptomatic patients 2

Site-specific cultures 1, 4:

• Based on suspected infection source identified above
• Urinalysis/culture only if urinary symptoms present 3

Imaging 2:

• Chest X-ray if respiratory symptoms
• CT abdomen/pelvis if abdominal source suspected
• Directed at suspected infection site

Treatment Algorithm

If Patient is Hemodynamically Stable and Asymptomatic:

• Complete diagnostic workup BEFORE initiating antibiotics 2
• Monitor closely for development of symptoms or vital sign changes
• Repeat CBC with manual differential in 24-48 hours if no source identified 5

If Sepsis Criteria Present:

• Initiate broad-spectrum empiric antibiotics within 1 hour of recognition 2
• Aggressive fluid resuscitation for hypotension 2
• Vasopressor support if hypotension persists despite fluids 2
• Source control measures (drainage of abscesses, removal of infected catheters) 2

If Specific Infection Source Identified Without Sepsis:

• Initiate appropriate empiric antibiotics based on suspected source and local resistance patterns after obtaining cultures 4

Critical Pitfalls to Avoid

• Do NOT ignore elevated neutrophil count when total WBC is only mildly elevated—left shift can occur with normal WBC and still indicate serious bacterial infection 2, 4
• Do NOT rely on automated analyzer alone—manual differential is essential to assess band forms 3, 2, 4
• Do NOT delay antibiotics in severe sepsis/septic shock while awaiting culture results 2
• Do NOT treat based solely on laboratory findings without clinical correlation if patient is asymptomatic and hemodynamically stable 2
• Do NOT obtain urine cultures in asymptomatic patients—asymptomatic bacteriuria is common (15-50% in elderly) and does not require treatment 3

Alternative Non-Infectious Causes to Consider

If no infection source is identified after thorough evaluation, consider 5, 6:

• Medications: lithium, beta-agonists, epinephrine 1, 4
• Obesity: can cause chronic mild neutrophilia with elevated inflammatory markers 6
• Smoking: chronic inflammatory state 5
• Recent stressors: surgery, exercise, trauma, emotional stress (can double WBC within hours) 5
• Chronic inflammatory conditions 5

However, given the degree of neutrophilia (89.3%), bacterial infection remains the most likely diagnosis and must be excluded first 1.