Interpretation of White Blood Cell Count
The white blood cell count of 20,000 cells per microliter is elevated for any patient (option C), indicating a significant leukocytosis that requires clinical attention.
Calculation and Analysis
To determine the white blood cell count from the hemocytometer data:
- Four large corner squares counted: 95,102,105, and 98 white cells
- Dilution factor: 1:20
- Formula for WBC calculation: (Sum of cells counted ÷ Number of squares) × Dilution factor × 10⁴
Calculation:
- Sum of cells counted = 95 + 102 + 105 + 98 = 400
- Number of squares = 4
- WBC = (400 ÷ 4) × 20 × 10⁴ = 100 × 20 × 10⁴ = 20,000 cells/μL
Clinical Significance
A white blood cell count of 20,000 cells/μL is significantly elevated compared to normal reference ranges:
- Normal WBC range for adults: 4,000-11,000 cells/μL 1
- Normal WBC range for infants: 6,000-17,000 cells/μL 1
This count exceeds normal ranges for both adults and infants, representing a clinically significant leukocytosis that warrants further evaluation.
Differential Diagnosis of Leukocytosis
Infectious Causes
- Bacterial infections (most common cause of marked leukocytosis)
- Severe viral infections
- Fungal infections
A WBC count >14,000 cells/mm³ has a likelihood ratio of 3.7 for bacterial infection 1.
Inflammatory Causes
- Tissue injury or necrosis
- Inflammatory disorders
- Autoimmune conditions
Physiologic or Stress-Induced
- Physical stress (seizures, anesthesia, overexertion)
- Emotional stress
- Post-surgical state
Medication-Related
- Corticosteroids
- Lithium
- Beta agonists 2
Hematologic Disorders
- Leukemia (acute or chronic)
- Myeloproliferative disorders
Clinical Implications
A WBC count of 20,000 cells/μL requires:
- Immediate clinical correlation with patient symptoms, vital signs, and physical examination
- Complete blood count with differential to assess for left shift (increased band neutrophils >6% or >1,500 cells/mm³) 1
- Evaluation for infection source including appropriate cultures and imaging based on clinical presentation
- Assessment for non-infectious causes if infection workup is negative
Warning Signs
Special attention should be given if the patient has:
- Concurrent abnormalities in red blood cell or platelet counts
- Weight loss, bleeding, or bruising
- Liver, spleen, or lymph node enlargement
- Immunosuppression
These findings increase suspicion for primary bone marrow disorders 2.
Critical Value Consideration
While 20,000 cells/μL represents significant leukocytosis, it does not reach the critical threshold of 100,000 cells/μL, which would constitute a medical emergency due to risk of brain infarction and hemorrhage 2.
In summary, a WBC count of 20,000 cells/μL is elevated for any patient regardless of age and requires prompt clinical evaluation to determine the underlying cause.