What infections cause eosinopenia?

Infections That Cause Eosinopenia

Bacterial sepsis and COVID-19 are the most significant infections that reliably cause eosinopenia, with eosinopenia being a valuable marker for both disease severity and diagnosis in these conditions.

Bacterial Infections

Sepsis

• Eosinopenia (<50 cells/mm³) is a reliable diagnostic marker for sepsis in critically ill patients 1
• Can distinguish between non-infection and infection with:
  • Sensitivity of 80%
  • Specificity of 91%
  • Positive likelihood ratio of 9.12
• Particularly useful in ICU settings as an early diagnostic tool
• Mechanism: Likely related to acute inflammatory response and cytokine-mediated eosinophil margination

Viral Infections

COVID-19

• COVID-19 consistently causes eosinopenia, even in patients with pre-existing eosinophilia 2, 3
• Eosinopenia severity correlates with disease severity:
  • Absolute eosinopenia is associated with higher need for intensive respiratory support (49.3% vs 13.3%) 3
  • Higher mortality (30.6% vs 6.2%) 3
  • Lower rate of hospital discharge (28% vs 65.6%) 3
• Extreme eosinopenia (0/mm³) is predictive of disease severity (aOR = 1.77) 4
• Eosinopenia occurs even before immunosuppressive treatment is initiated 2
• Mechanism: Likely related to direct viral effects and inflammatory cytokine response

Other Viral Infections

• While less well documented than COVID-19, other viral infections may cause transient eosinopenia during acute phases

Clinical Implications

Diagnostic Value

• Eosinopenia can serve as an early marker for:
  • Bacterial sepsis (cutoff <50 cells/mm³) 1
  • Severe COVID-19 (absolute eosinopenia) 3

Prognostic Value

• In COVID-19:
  • Absolute eosinopenia is an independent factor associated with:
    • 4-week mortality
    • Need for intensive respiratory support
    • Lower likelihood of hospital discharge 3

Special Consideration: Pre-existing Eosinophilia

• Even in patients with chronic eosinophilia (e.g., from strongyloidiasis), COVID-19 can cause complete resolution of eosinophilia 2
• Eosinophil levels typically return after recovery from the infection

Contrast with Eosinophilia-Causing Infections

While many infections cause eosinophilia (particularly parasitic infections like strongyloidiasis, schistosomiasis, and filariasis), it's important to recognize that bacterial sepsis and COVID-19 characteristically cause eosinopenia.

Clinical Applications

Monitoring Tool

• Serial eosinophil counts can help monitor disease progression in COVID-19 and sepsis
• Return of eosinophils may signal recovery from these infections

Screening Consideration

• In patients with unexplained eosinopenia, consider:
  • Bacterial sepsis workup
  • COVID-19 testing, particularly during pandemic conditions

Pitfalls and Caveats

• Eosinopenia is not specific to infections and can occur in other conditions:
  • Stress response
  • Corticosteroid administration
  • Acute inflammatory states
• While eosinopenia is predictive of COVID-19 severity, it is not consistently predictive of mortality in all studies 4
• Interpretation should always be in clinical context with other laboratory and clinical parameters

Remember that while eosinopenia is a valuable marker, it should be interpreted alongside other clinical and laboratory findings for optimal diagnostic accuracy.