Characterization of treatment failure in efficacy trials of drugs against Plasmodium vivax by genotyping neutral and drug resistance-associated markers.

Plasmodium vivax intervention trials customarily report uncorrected treatment failure rates. Application of recrudescence-reinfection genotyping and drug resistance single-nucleotide polymorphism typing to a 4-arm comparative efficacy trial illustrated that molecular approaches can assist in understanding the relative contributions of true drug resistance (recurrent with same genotype) and new infections to treatment failure. The PCR-corrected adequate clinical and parasitologic response may constitute an informative secondary endpoint in future P. vivax drug trials.