What is the frequency of neutrophilia (elevated neutrophil count) in malaria?

Neutrophilia in Malaria: Prevalence and Clinical Significance

Neutrophilia is uncommon in malaria infections, with thrombocytopenia being the predominant hematological finding in 70-79% of malaria cases. 1 When neutrophilia does occur, it is more frequently associated with severe disease and complications, particularly in Plasmodium falciparum infections.

Hematological Patterns in Malaria

Common Findings

• Thrombocytopenia: The most frequent laboratory finding in malaria (70-79% of cases), regardless of Plasmodium species 2, 1
• Normal or decreased white cell count: Most patients with malaria present with normal or low total white blood cell counts
• Hyperbilirubinemia: Present in approximately 38% of cases (sensitivity 38%, specificity 95%) 1

Neutrophil Patterns in Different Malaria Types

Uncomplicated Malaria

• Typically shows normal or slightly decreased neutrophil counts
• In patients with prior repeated infections, absolute neutrophil counts positively correlate with parasitemia 3
• Monocyte to neutrophil ratio is negatively correlated with parasitemia in patients with prior repeated infections 3

Complicated/Severe Malaria

• Neutrophilia may be present, particularly in severe P. falciparum infections
• Neutrophil activation markers (neutrophil elastase, citrullinated histone, neutrophil extracellular traps) increase with disease severity 4
• Low monocyte to neutrophil ratio is associated with disease complications in primary P. falciparum infection 3

Clinical Significance of Neutrophil Changes

Prognostic Implications

• Toxic granulation of neutrophils: Seen exclusively in P. falciparum malaria and significantly associated with:

  • Anemia
  • Jaundice
  • Cerebral involvement
  • Adult respiratory distress syndrome
  • Renal dysfunction
  • Higher mortality 5

• Band cells: More frequently observed in P. falciparum than P. vivax malaria, indicating left shift 5

• Neutrophilia in P. knowlesi: Associated with increased risk of acute lung injury (adjusted odds ratio 3.27) 4

Pathophysiological Role

• Neutrophils participate in defense against malaria parasites through:

  • Phagocytosis
  • Reactive oxygen species production
  • Release of neutrophil extracellular traps (NETs) 6, 7

• However, neutrophils may also contribute to pathogenesis through:

  • Release of toxic granules
  • Excessive NET formation leading to tissue damage
  • Endothelial activation 4, 6, 7

Monitoring and Management Implications

• Thrombocytopenia (<150,000/μL) should prompt malaria screening in appropriate clinical contexts 2, 1
• Presence of neutrophilia and toxic granulation in P. falciparum malaria should raise concern for severe disease 5
• Neutrophil activation markers correlate with endothelial activation and may contribute to complications like acute lung injury 4
• After treatment, absolute monocyte counts and monocyte to neutrophil ratio typically increase, while absolute neutrophil counts decrease 3

Clinical Pitfalls and Caveats

• Relying solely on white cell differential for malaria diagnosis is inadequate; microscopic examination of thick and thin blood films remains the gold standard 2, 1
• Neutrophilia in malaria may be misinterpreted as bacterial infection, potentially leading to unnecessary antibiotic use
• Secondary bacterial infections can occur in malaria patients, complicating the interpretation of neutrophilia 2
• Malaria parasites can inhibit neutrophil antimicrobial functions, making patients more susceptible to secondary opportunistic infections like Salmonella 6

In conclusion, while neutrophilia is not a common finding in malaria, when present, particularly with toxic granulation, it may indicate severe disease and complications, especially in P. falciparum infections. Clinicians should be vigilant about this finding as it may have prognostic implications.