Is a fever with a white blood cell (WBC) count of 18,600 considered normal?

Fever with WBC Count of 18,600 is Abnormal and Suggests Bacterial Infection

A white blood cell count of 18,600 with fever is definitely abnormal and strongly suggests a bacterial infection requiring further evaluation and likely treatment. 1

Understanding WBC Elevation in Fever

When evaluating fever with leukocytosis (elevated WBC count), several important diagnostic considerations apply:

• A WBC count >14,000 cells/mm³ has a likelihood ratio of 3.7 for bacterial infection 1
• The presence of bands >1,500 cells/mm³ or band neutrophils >16% significantly increases the likelihood of bacterial infection (likelihood ratios of 14.5 and 4.7, respectively) 1

Key Diagnostic Indicators:

• WBC count of 18,600 significantly exceeds the normal range of 4,000-10,000/L
• The combination of fever with this degree of leukocytosis strongly points to an infectious process, particularly bacterial 2

Evaluation Algorithm

1. Immediate Assessment:

   • Complete blood count with differential to assess for left shift (bands >16% or band count >1,500 cells/mm³) 2, 1
   • Blood cultures should be obtained before antibiotic administration 2
   • Additional inflammatory markers (CRP, ESR, procalcitonin) to help distinguish bacterial from non-bacterial causes 1

2. Source Identification:

   • Respiratory assessment (consider chest radiograph if respiratory symptoms present) 2
   • Urinalysis and urine culture if urinary symptoms present 1
   • Stool studies if gastrointestinal symptoms present 1
   • Skin and soft tissue examination for cellulitis or abscess

3. Risk Stratification:

   • Assess for signs of sepsis (hypotension, tachycardia, altered mental status)
   • Evaluate oxygenation (pulse oximetry) if respiratory rate >25 breaths/minute 2
   • Consider comorbidities that may affect interpretation (diabetes, immunosuppression)

Clinical Implications

While a WBC count of 18,600 with fever is abnormal, it's important to note that:

• The degree of leukocytosis doesn't always correlate with severity of infection 3
• Some patients with bacteremia may present with normal WBC counts (52% in one study) 3
• The clinical context and other vital signs are crucial for complete assessment

Common Pitfalls to Avoid

1. Don't rely solely on WBC count: While a count of 18,600 is significantly elevated, some bacterial infections may present with normal WBC counts 3

2. Don't dismiss infection with normal temperature: 33% of patients with bacteremia can have normal body temperature 3

3. Don't overlook non-infectious causes: While infection is most likely, consider other causes of leukocytosis such as:

   • Stress response (trauma, surgery, emotional stress) 4
   • Medication effects (corticosteroids, epinephrine) 4
   • Inflammatory conditions 4

4. Don't miss special populations: Infants, elderly, and immunocompromised patients may have atypical presentations 2

In conclusion, a WBC count of 18,600 with fever represents a significant abnormality that warrants thorough evaluation for infection, with bacterial causes being the most likely etiology requiring prompt treatment.