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Loop mediated isothermal amplification (LAMP) accurately detects malaria DNA from filter paper blood samples of low density parasitaemias.

Aydin-Schmidt B, Xu W, González IJ, Polley SD, Bell D, Shakely D, Msellem MI, Björkman A, Mårtensson A - PLoS ONE (2014)

Bottom Line: Samples were amplified at 65°C for 40 minutes in a real-time turbidimeter and results were compared with nested PCR.The real-time PCR corrected nested PCR result was defined as gold standard.The specificities for both Pan and Pf-LAMP were 100% (95%CI 99.1-100) in both study groups.

View Article: PubMed Central - PubMed

Affiliation: Malaria Research, Department of Microbiology, Tumor and Cellbiology, Karolinska Institutet, Stockholm, Sweden; Unit of infectious diseases, Karolinska University Hospital, Stockholm, Sweden.

ABSTRACT

Background: Loop mediated isothermal amplification (LAMP) provides an opportunity for improved, field-friendly detection of malaria infections in endemic areas. However data on the diagnostic accuracy of LAMP for active case detection, particularly low-density parasitaemias, are lacking. We therefore evaluated the performance of a new LAMP kit compared with PCR using DNA from filter paper blood spots.

Methods and findings: Samples from 865 fever patients and 465 asymptomatic individuals collected in Zanzibar were analysed for Pan (all species) and Pf (P. falciparum) DNA with the Loopamp MALARIA Pan/Pf kit. Samples were amplified at 65°C for 40 minutes in a real-time turbidimeter and results were compared with nested PCR. Samples with discordant results between LAMP and nested PCR were analysed with real-time PCR. The real-time PCR corrected nested PCR result was defined as gold standard. Among the 117 (13.5%) PCR detected P. falciparum infections from fever patients (mean parasite density 7491/µL, range 6-782,400) 115, 115 and 111 were positive by Pan-LAMP, Pf-LAMP and nested PCR, respectively. The sensitivities were 98.3% (95%CI 94-99.8) for both Pan and Pf-LAMP. Among the 54 (11.6%) PCR positive samples from asymptomatic individuals (mean parasite density 10/µL, range 0-4972) Pf-LAMP had a sensitivity of 92.7% (95%CI 80.1-98.5) for detection of the 41 P. falciparum infections. Pan-LAMP had sensitivities of 97% (95%CI 84.2-99.9) and 76.9% (95%CI 46.2-95) for detection of P. falciparum and P. malariae, respectively. The specificities for both Pan and Pf-LAMP were 100% (95%CI 99.1-100) in both study groups.

Conclusion: Both components of the Loopamp MALARIA Pan/Pf detection kit revealed high diagnostic accuracy for parasite detection among fever patients and importantly also among asymptomatic individuals of low parasite densities from minute blood volumes preserved on filter paper. These data support LAMPs potential role for improved detection of low-density malaria infections in pre-elimination settings.

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Related in: MedlinePlus

Flow chart of study. Reference standard = Cytochrome B nested PCR. Gold standard = Cytochrome B real-time PCR corrected nested PCR.
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pone-0103905-g001: Flow chart of study. Reference standard = Cytochrome B nested PCR. Gold standard = Cytochrome B real-time PCR corrected nested PCR.

Mentions: Baseline characteristics of the included subjects are presented in Table 1 and the study flow is outlined in Figure 1.


Loop mediated isothermal amplification (LAMP) accurately detects malaria DNA from filter paper blood samples of low density parasitaemias.

Aydin-Schmidt B, Xu W, González IJ, Polley SD, Bell D, Shakely D, Msellem MI, Björkman A, Mårtensson A - PLoS ONE (2014)

Flow chart of study. Reference standard = Cytochrome B nested PCR. Gold standard = Cytochrome B real-time PCR corrected nested PCR.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126669&req=5

pone-0103905-g001: Flow chart of study. Reference standard = Cytochrome B nested PCR. Gold standard = Cytochrome B real-time PCR corrected nested PCR.
Mentions: Baseline characteristics of the included subjects are presented in Table 1 and the study flow is outlined in Figure 1.

Bottom Line: Samples were amplified at 65°C for 40 minutes in a real-time turbidimeter and results were compared with nested PCR.The real-time PCR corrected nested PCR result was defined as gold standard.The specificities for both Pan and Pf-LAMP were 100% (95%CI 99.1-100) in both study groups.

View Article: PubMed Central - PubMed

Affiliation: Malaria Research, Department of Microbiology, Tumor and Cellbiology, Karolinska Institutet, Stockholm, Sweden; Unit of infectious diseases, Karolinska University Hospital, Stockholm, Sweden.

ABSTRACT

Background: Loop mediated isothermal amplification (LAMP) provides an opportunity for improved, field-friendly detection of malaria infections in endemic areas. However data on the diagnostic accuracy of LAMP for active case detection, particularly low-density parasitaemias, are lacking. We therefore evaluated the performance of a new LAMP kit compared with PCR using DNA from filter paper blood spots.

Methods and findings: Samples from 865 fever patients and 465 asymptomatic individuals collected in Zanzibar were analysed for Pan (all species) and Pf (P. falciparum) DNA with the Loopamp MALARIA Pan/Pf kit. Samples were amplified at 65°C for 40 minutes in a real-time turbidimeter and results were compared with nested PCR. Samples with discordant results between LAMP and nested PCR were analysed with real-time PCR. The real-time PCR corrected nested PCR result was defined as gold standard. Among the 117 (13.5%) PCR detected P. falciparum infections from fever patients (mean parasite density 7491/µL, range 6-782,400) 115, 115 and 111 were positive by Pan-LAMP, Pf-LAMP and nested PCR, respectively. The sensitivities were 98.3% (95%CI 94-99.8) for both Pan and Pf-LAMP. Among the 54 (11.6%) PCR positive samples from asymptomatic individuals (mean parasite density 10/µL, range 0-4972) Pf-LAMP had a sensitivity of 92.7% (95%CI 80.1-98.5) for detection of the 41 P. falciparum infections. Pan-LAMP had sensitivities of 97% (95%CI 84.2-99.9) and 76.9% (95%CI 46.2-95) for detection of P. falciparum and P. malariae, respectively. The specificities for both Pan and Pf-LAMP were 100% (95%CI 99.1-100) in both study groups.

Conclusion: Both components of the Loopamp MALARIA Pan/Pf detection kit revealed high diagnostic accuracy for parasite detection among fever patients and importantly also among asymptomatic individuals of low parasite densities from minute blood volumes preserved on filter paper. These data support LAMPs potential role for improved detection of low-density malaria infections in pre-elimination settings.

Show MeSH
Related in: MedlinePlus