Predictors of Treatment Failure in Multiple Drug-resistant Falciparum Malaria: Results from a 42-day Follow-up of 224 Patients in Eastern Thailand

We report here the results of a 42-day follow-up of 224 patients treated with mefloquine for uncomplicated falciparum malaria in Eastern Thailand. The risk of treatment failure among the 209 patients who completed the follow-up was 57% (95% confidence interval [CI] = 50,64). The daily risk of treatment failure, estimated through an exponential survival function, was constant during the follow-up period and equal to 1.9%. Five patient characteristics were found to be independent and important predictors of treatment failure in a Cox proportional hazards model: a young age (adjusted hazard ratio [AHR] for an increase of 10 years of age = 0.75 [95% CI = 0.62, 0.90]); a history of at least three documented mefloquine treatments in the past year (AHR = 1.89 [95% CI = 1.10, 3.24]); a parasitemia count > 100,000/microliter (AHR = 1.80 [95% CI = 1.16, 2.80]); and a history of diarrhea in the first two days after treatment (AHR = 1.51 [95% CI = 0.99, 2.31]). A hemoglobin level < or = 10 g/dl on the day of consultation was also a predictor of treatment failure, but only among patients who had been treated for malaria in the past 120 days (AHR = 4.38 [95% CI = 1.55, 12.1]). These latter patients may have become anemic while they were unsuccessfully treated with mefloquine for an infection by a multiple drug-resistant strain in the past 120 days.(ABSTRACT TRUNCATED AT 250 WORDS)