Highly sensitive detection of malaria parasitemia in a malaria-endemic setting: performance of a new loop-mediated isothermal amplification kit in a remote clinic in Uganda.

Authors:
Heidi Hopkins
Heidi Hopkins
University of California
United States
Spencer D Polley
Spencer D Polley
London School of Hygiene and Tropical Medicine
United Kingdom
Bosco Agaba
Bosco Agaba
Mr
Epidemiologist
Cape Town | S.Africa
Daniel J Kyabayinze
Daniel J Kyabayinze
Université Victor Segalen
France

J Infect Dis 2013 Aug 30;208(4):645-52. Epub 2013 Apr 30.

Foundation for Innovative New Diagnostics, Uganda Ministry of Health, Kampala, Uganda.

Background: Current malaria diagnostic tests, including microscopy and antigen-detecting rapid tests, cannot reliably detect low-density infections. Molecular methods such as polymerase chain reaction (PCR) are highly sensitive but remain too complex for field deployment. A new commercial molecular assay based on loop-mediated isothermal amplification (LAMP) was assessed for field use.

Methods: Malaria LAMP (Eiken Chemical, Japan) was evaluated for samples from 272 outpatients at a rural Ugandan clinic and compared with expert microscopy, nested PCR, and quantitative PCR (qPCR). Two technicians performed the assay after 3 days of training, using 2 alternative blood sample-preparation methods and visual interpretation of results by fluorescence assay.

Results: Compared with 3-well nested PCR, the sensitivity of both LAMP and single-well nested PCR was 90%; the microscopy sensitivity was 51%. For samples with a Plasmodium falciparum qPCR titer of ≥ 2 parasites/µL, LAMP sensitivity was 97.8% (95% confidence interval, 93.7%-99.5%). Most false-negative LAMP results involved samples with parasitemia levels detectable by 3-well nested PCR but very low or undetectable by qPCR.

Conclusions: Malaria LAMP in a remote Ugandan clinic achieved sensitivity similar to that of single-well nested PCR in a United Kingdom reference laboratory. LAMP dramatically lowers the detection threshold achievable in malaria-endemic settings, providing a new tool for diagnosis, surveillance, and screening in elimination strategies.

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Source
https://academic.oup.com/jid/article-lookup/doi/10.1093/infd
Publisher Site
http://dx.doi.org/10.1093/infdis/jit184DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3719898PMC

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August 2013
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