Chloroquine treatment of uncomplicated Plasmodium falciparum malaria in Mali: parasitologic resistance versus therapeutic efficacy

Whether and when to replace chloroquine with other antimalarial drugs is an urgent public health question in much of Africa, where Plasmodium falciparum, which is increasingly resistant to chloroquine, continues to kill millions each year. Antimalarial drug efficacy has traditionally been measured as parasitologic resistance, but recent guidelines use both clinical and parasitologic criteria to monitor therapeutic efficacy. To assess the new efficacy protocol, we measured parasitologic and therapeutic outcomes in 514 patients treated with chloroquine for uncomplicated P. falciparum malaria in Mali. There was a general agreement between parasitologic and therapeutic outcomes at two sites, with 13-17% parasitologic resistance rates and 10-15% treatment failure rates. However, the new protocol overestimated early treatment failure rates (21-71% of cases classified as early treatment failure had sensitive or RI parasitologic responses), particularly where resistance was rare, and missed low-level parasitologic resistance. Modifications of the protocol for monitoring antimalarial therapeutic efficacy are recommended.