Determination of failure of treatment of plasmodium falciparum infection by using polymerase chain reaction single-strand conformational polymorphism fingerprinting.

The inability to distinguish failures of treatment of Plasmodium falciparum infection from new infections is an important impediment to the evaluation of antimalarial drugs. On the basis of a pilot study utilizing polymerase chain reaction (PCR) single-strand conformational polymorphism (SSCP) analysis to genotype P. falciparum isolates, we sought to confirm that PCR SSCP analysis could reliably distinguish infections for which treatment failed from unrelated infections with a sample size adequate to estimate the accuracy of this technique. PCR SSCP analysis of the MSP-1, MSP-2, and GLURP genes was performed on 72 paired isolates recovered from 36 individuals for whom treatment failed in Thailand. In every case (100% [95% confidence interval (CI), 90%-100%]), the PCR SSCP pattern of the recrudescent isolates matched that of the primary isolate. We determined whether PCR SSCP analysis could separate unrelated infections by comparing each recrudescent isolate with each of the unrelated primary isolates. Of 1,260 comparisons, 1,258 (99.8% [95% CI, 99.4%-100%]) were unique. The results indicate that PCR SSCP analysis can be used to differentiate infections for which treatment failed from reinfections.