Prospective comparison of methods for the early prediction of treatment failure in patients with falciparum malaria.

The prompt identification of patients with falciparum malaria who are at risk of late therapeutic failure could help clinicians avoid the dangers of missed or delayed retreatment. Different methods for predicting late recrudescence were compared for 52 patients whose parasitemia initially cleared after treatment with either halofantrine or quinine. Parasites reappeared in the peripheral circulation of six individuals 17 to 28 days after the initiation of therapy. Transient rises in parasite counts on thick blood films were accurate (91% specific and 100% sensitive) and prompt indicators of eventual recrudescence. All six therapeutic failures had been predicted by the third day (mean time [+/- SEM], 51.5 +/- 3.6 hours) after initiation of treatment. Parasite clearance time, fever clearance time, rRNA probe, and the polymerase chain reaction had less practical prognostic value. Serial thick-film parasite counts are a simple, cheap, rapid, and reliable method for identifying patients at high risk of recrudescence.