What are the causes of bandemia?

Causes of Bandemia

Bandemia, defined as an elevated percentage of immature neutrophils (band cells) in the blood (>10%), is most commonly caused by infections, particularly bacterial infections, but can also result from tissue damage, inflammation, and certain hematologic disorders.

Primary Causes of Bandemia

Infectious Causes

• Bacterial infections - Most common cause of bandemia
  • Sepsis and severe sepsis 1, 2
  • Clostridioides difficile colitis 3
  • Pneumonia
  • Urinary tract infections
  • Intra-abdominal infections
  • Skin and soft tissue infections

Inflammatory Conditions

• Tissue damage/trauma - Major trauma is associated with significant bandemia 4
• Post-surgical states - Major elective surgery can trigger bandemia 4
• Burns
• Inflammatory disorders
• Cerebrovascular accidents - Can trigger bandemia even without infection 4

Hematologic Disorders

• Myeloproliferative disorders
• Hemolytic anemias 3
  • Hemolytic-uremic syndrome
  • Thrombotic thrombocytopenic purpura
  • Paroxysmal nocturnal hemoglobinuria
• Iron deficiency anemia - Can present with bandemia 3

Drug-Induced Causes

• Medications that can cause bandemia:
  • Certain antibiotics
  • Chemotherapeutic agents 3
  • Heparin 3
  • Corticosteroids

Other Causes

• Pregnancy - Normal physiologic changes can cause mild bandemia 3
• Stress response - Physical or emotional stress
• Metabolic disorders
  • Hyperammonemia 3
  • Uremia

Clinical Significance of Bandemia

Prognostic Value

• Bandemia is associated with increased mortality risk, particularly in sepsis 1, 2
• Severe bandemia (>18%) in patients discharged from the ED is associated with a 5-times higher 30-day mortality rate compared to non-bandemic patients 2
• Bandemia without leukocytosis still carries significant risk for adverse outcomes:
  • 4.4% develop sepsis within 7 days
  • 2.4% progress to severe sepsis
  • 1.5% develop bacteremia
  • 0.58% mortality within 7 days 5

Predictors of Poor Outcomes with Bandemia

• Concurrent tachycardia or fever 2
• Severe bandemia (>17%) 1
• Bandemia in the context of:
  • Age >70 years
  • Severe leukocytosis (≥35,000/μL) or leukopenia (<4,000/μL)
  • Cardiorespiratory failure
  • Thrombocytopenia (platelet count <150 × 100/mm³)
  • Coagulopathy (INR >2.0)
  • Renal insufficiency (BUN >40 mg/dL) 3

Evaluation of Bandemia

Laboratory Assessment

• Complete blood count with differential
• Blood cultures if infection suspected
• Inflammatory markers (CRP, ESR, procalcitonin)
• Specific tests based on suspected cause:
  • Iron studies for anemia evaluation 3
  • Liver and kidney function tests
  • Ammonia levels if hyperammonemia suspected 3

Clinical Correlation

• Bandemia should be interpreted in the context of:
  • Patient symptoms
  • Vital signs
  • Other laboratory abnormalities
  • Clinical presentation

Important Considerations

1. Bandemia can occur without leukocytosis and still indicate serious underlying pathology 5
2. The trend of bandemia over time may be more important than a single measurement 1
3. Bandemia in the context of tissue damage (trauma, surgery, stroke) may not necessarily indicate infection 4
4. Persistent bandemia despite appropriate antibiotic therapy may indicate persistent inflammation-immunosuppression and catabolism syndrome (PICS) rather than ongoing infection 4

Common Pitfalls

1. Overlooking bandemia when WBC count is normal - Bandemia without leukocytosis still carries significant risk for adverse outcomes 5
2. Attributing bandemia solely to infection - Multiple non-infectious causes exist 4
3. Overuse of antibiotics - Prolonged empiric antibiotic use in patients with persistent bandemia without evidence of infection may lead to antibiotic resistance and C. difficile infections 4
4. Ignoring trends - The trend of bandemia over time may be more clinically relevant than a single measurement 1

In summary, while infection remains the most common cause of bandemia, clinicians should maintain a broad differential diagnosis and consider non-infectious causes, particularly in patients with recent trauma, surgery, or other conditions associated with tissue damage and inflammation.