Thrombocytopenia as Additional Marker of Severity in African Children with Plasmodium Falciparum Malaria

Background: Thrombocytopenia (platelets counts < 100,000/mm3) is predictive of death in African children with falciparum malaria exposed to low seasonal transmission. However, the impact of this indicator on malaria severity was not fully addressed. Method: We compared platelet counts according to multiple indicators of malaria severity including 1990 and 2000 World Health Organization (WHO) criteria, 24-hour Pediatric Risk of Mortality (PRISM) score, 24-hour Paediatric Logistic Organ dysfunction (PELOD) score, and Major Therapeutic Procedures (MTPs), defined as requirement for mechanical ventilation, hemodynamic support, blood transfusion, hemodialysis, or use of sedatives drugs. We next assessed the discriminatory performance of thrombocytopenia, alone or together with a combination of WHO 2000 criteria in predicting these outcomes. Result: Children fulfilling both WHO definitions of severe malaria had lower mean platelet counts than mild cases in accordance with both (129,000 versus 173,000/mm3; P<0.001). Thrombocytopenic children had higher mean PRISMh24 and PELODh24 admission scores than non-thrombocytopenic counterparts (5.8 versus 4.6; P<0.01; 6.2 versus 4.6; P<0.001, respectively). They did not need more MTPs (63.0% vs 52.6%, P=0.07). Among 288 children, the combination of impaired consciousness, respiratory distress, or thrombocytopenia, had the same discriminatory performance in predicting outcome than WHO 2000 criteria (sensitivity, 100%, specificity, 28%, positive predictive value, 80%, negative predictive value, 100%). Conclusion: Thrombocytopenia is an indicator of life-threatening malaria and should therefore be proposed as additional marker of severity, especially in non-immune African children.