Empiric Antibiotic Therapy for Leukocytosis of Unknown Cause
Diagnostic Approach for Leukocytosis
- Leukocytosis alone without specific signs of infection does not warrant empiric antibiotic therapy, as this may mask the underlying cause and lead to inappropriate treatment 1
- A complete blood cell count with differential should be performed to assess for left shift (≥16% bands or total band count ≥1500 cells/mm³), which would suggest bacterial infection 1
- In the absence of fever, specific clinical manifestations of a focal infection, or significant left shift, additional diagnostic tests should be performed before starting antibiotics 1
- Blood cultures should be obtained before starting antibiotics if bacteremia is suspected 1
When Antibiotics Are Indicated
- Empiric antibiotics should only be initiated when there is clinical evidence of infection such as fever and signs of systemic inflammation 2
- Empiric antibiotics should only be initiated when there is clinical evidence of infection such as specific signs of infection at a source (respiratory, urinary, skin, etc.) 3
- Empiric antibiotics should only be initiated when there is clinical evidence of infection such as evidence of sepsis or hemodynamic instability 4
- Empiric antibiotics should only be initiated when there is clinical evidence of infection such as neutropenic patients with fever or signs of infection 5
- For patients with suspected spontaneous bacterial peritonitis (SBP), antibiotics should be started only after diagnostic paracentesis confirms an ascitic fluid PMN count >250/mm³ 6
Risks of Inappropriate Antibiotic Use
- Premature antibiotic administration may mask the underlying cause of leukocytosis 7
- Premature antibiotic administration may lead to antibiotic resistance, particularly with the emergence of multidrug-resistant organisms 3
- Premature antibiotic administration may interfere with diagnostic cultures if obtained after antibiotic initiation 6