Determination of failure of treatment of Plasmodium falciparum infection by using polymerase chain reaction single-strand conformational polymorphismfingerprinting

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) analy sis to genotype P. falciparum isolates, we sought to confirm that PCR SSCP analysis could reliably distinguish infections for which treatment failed f rom unrelated infections with a sample size adequate to estimate the accura cy of this technique. PCR SSCP analysis of the MSP-1, MSP-2, and GLURP gene s was performed on 72 paired isolates recovered from 36 individuals for who m treatment failed in Thailand. In every case (100% [95% confidence interva l (CT), 90%-100%]), the PCR SSCP pattern of the recrudescent isolates match ed that of the primary isolate. Ne determined whether PCR SSCP analysis cou ld separate unrelated infections by comparing each recrudescent isolate wit h 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 ana lysis can be used to differentiate infections for which treatment failed fr om reinfections.