Distinction of Plasmodium falciparum recrudescence and re-infection by MSP2 genotyping: a caution about unstandardized classification criteria.
Malar J
; 7: 185, 2008 Sep 23.
Article
em En
| MEDLINE
| ID: mdl-18811949
ABSTRACT
BACKGROUND:
Plasmodium falciparum genotyping with molecular polymorphic markers is widely employed to distinguish recrudescence from re-infection in antimalarial drug efficacy monitoring programmes. However, limitations occur on agarose gel DNA measurements used to resolve the polymorphisms. Without empirical data, the current distinction of pre- and post-treatment bands, as persistent or new infection, is subjective and often varying by author. This study measures empirical tolerance limits for classifying different-sized bands as same or different alleles during MSP2 genotyping.METHODS:
P. falciparum field samples from 161 volunteers were genotyped by nested PCR using polymorphic MSP2 family-specific primers. Data were analysed to determine variability of band size measurements between identical MSP2 alleles randomized into different agarose lanes.RESULTS:
The mean (95% CI) paired difference in band size between identical alleles was 9.8 bp (1.48 - 18.16 bp, p = 0.022) for 3D7/IC and 2.54 (-3.04 - 8.05 bp, p = 0.362) for FC27. Based on these findings, pre- and post-treatment samples with 3D7/IC alleles showing less than 18 bp difference corresponded to recrudescence, with 95% confidence, while greater difference indicated new infection. FC27 allele differences were much narrower. For both 3D7/IC and FC27 amplicon, allele detection sensitivity was significantly higher with 13 mul compared to 20 mul or 30 mul lane loading volumes.CONCLUSION:
During MSP genotyping, it is useful to standardize classifications against measurement of background variability on identical alleles, in order to obtain reliable findings. It is critical to use a fixed optimal lane loading volume for constant allele patency, to avoid the disappearance or false appearance of new infection.
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Base de dados:
MEDLINE
Assunto principal:
Plasmodium falciparum
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Proteínas de Protozoários
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Reação em Cadeia da Polimerase
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Impressões Digitais de DNA
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Malária Falciparum
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Eletroforese em Gel de Ágar
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Antígenos de Protozoários
Tipo de estudo:
Clinical_trials
Limite:
Adolescent
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Adult
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Animals
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Child
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Child, preschool
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Female
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Humans
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Male
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Middle aged
Idioma:
En
Ano de publicação:
2008
Tipo de documento:
Article