What can increase White Blood Cell (WBC) count besides infection?

Causes of Elevated White Blood Cell Count Besides Infection

Numerous non-infectious conditions can cause elevated white blood cell (WBC) counts, including medications (particularly corticosteroids), stress, inflammation, malignancies, and certain physiological states. 1, 2

Medication-Related Causes

• Corticosteroids: Can cause significant leukocytosis, with increases up to 4.84 × 10^9/L WBCs within 48 hours after high-dose administration 3
• Other medications associated with leukocytosis include:
  • Lithium
  • Beta-agonists
  • Epinephrine
  • Granulocyte colony-stimulating factors

Physiological and Stress-Related Causes

• Physical stress: Exercise, seizures, anesthesia, overexertion 2
• Emotional stress: Acute psychological stressors 2
• Surgery and trauma: Can cause rapid mobilization from bone marrow storage and marginated pools 4
• Pregnancy: Requires use of pregnancy-specific normal ranges 4

Inflammatory Conditions (Non-Infectious)

• Inflammatory bowel disease (IBD) 1
• Rheumatoid arthritis and other autoimmune disorders
• Vasculitis
• Tissue injury or necrosis

Hematologic and Malignant Causes

• Acute leukemias: Often present with illness and very high WBC counts
• Chronic leukemias: Often diagnosed incidentally due to abnormal blood counts
• Myeloproliferative disorders
• Lymphomas

Note: WBC counts above 100,000 per mm³ represent a medical emergency due to risk of brain infarction and hemorrhage 2

Other Notable Causes

• Smoking: Associated with chronic elevation in WBC count 4
• Obesity: Higher BMI correlates with higher WBC counts 5
• Asplenia: Absence of spleen function 4
• Age-related factors: WBC counts tend to decrease with age 5
• Racial differences: Studies show Black individuals may have lower baseline WBC counts than White individuals 5

Clinical Pearls for Interpretation

• Normal WBC range in hospitalized patients without infection may be wider (1.6-14.5 × 10^9/L) than traditional reference ranges 5
• Comorbidities like diabetes, chronic kidney disease, and COPD are associated with higher baseline WBC counts 5
• Serial monitoring of WBC counts is more valuable than a single measurement 6
• The leukocyte differential provides important clues:
  • Left shift (increased bands >6% or >1,500 cells/mm³) suggests infection 6
  • Eosinophilia suggests parasitic infection or allergic reaction 4
  • Lymphocytosis is common in viral illnesses, especially in children 4

When to Suspect Malignancy

Be particularly concerned about hematologic malignancy when elevated WBC count is accompanied by:

• Concurrent abnormalities in red blood cell or platelet counts
• Weight loss, fever, night sweats
• Unexplained bleeding or bruising
• Liver, spleen, or lymph node enlargement
• Extreme elevations in WBC count without obvious cause 2

Remember that while infections are the most common cause of leukocytosis, considering these non-infectious etiologies is crucial for accurate diagnosis and appropriate management.