Imen Hammami

Propriétés statistiques des estimateurs de la charge parasitaire dans les études portant sur le paludisme et applications opérationnelles.

mardi 31 mai 2011, 14h30 - 15h30

Salle de réunion, espace Turing

Malaria is a global health problem responsible for nearly 3 million deaths each year, an average of one person every 12s. In addition, 300 to 500 million people contract the disease each year. The level of infection, expressed as the parasite density (PD), is classically defined as the number of asexual forms of Plasmodium falciparum relative to a microliter of blood. Microscopy of Giemsa-stained thick blood films is the gold standard for parasite enumeration in case of febrile episodes. PD estimation methods usually involve threshold values as the number of white blood cells (WBC) counted and the number high power fields (HPF) seen. However, the statistical properties of PD estimates generated by these methods have been generally overlooked.
We are interested in the statistical properties (bias, variance, False-Negative Rates…) of the PD estimates of commonly used threshold-based counting techniques according to varying threshold values. Furthermore, we give more insights on the behavior of measurement errors according to varying threshold values and on what would be the optimal threshold values that minimize the variability.
Keywords: Threshold-based counting techniques, parasite density estimators, bias,
variance, False-Positive Rates, cost-effectiveness, malaria epidemiology.