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London School of Hygiene & Tropical Medicine Malaria Centre

Better diagnostics for malaria elimination

 
Photograph courtesy of Dalia Iskander
 

Photograph courtesy of Dalia Iskander

02 December 2015
Researchers identify improvements in diagnostics that could help make malaria elimination a more realistic goal

Accurately detecting malaria parasites in people living in endemic countries will be a key component of many elimination strategies. Two papers in a special supplement in the journal Nature describe the limits of sensitivity of current diagnostics (Wu, et al 2015) and what detection limits newer diagnostics would need to have to impact on transmission (Slater, et al 2015).

In the first paper, London School of Hygiene & Tropical Medicine Malaria Centre researchers, Lindsey Wu and Lotus van den Hoogen, and colleagues from Imperial College London analysed more than 170,000 data records comparing different malaria diagnostic approaches. They showed that microscopy identifies approximately 90% of infections detected by rapid diagnostic tests (RDT). However, in turn, these RDTs identify only 40% of infections detected by sensitive molecular amplification methods.

The relevance of these infections is described in the second paper. This uses data collected from field studies conducted by Malaria Centre members and colleagues from Centre National de Recherche et de Formation sur le Paludisme (CNRFP) in Burkina Faso, to demonstrate that people with these low parasite density infections can pass on the malaria infection to mosquitoes, perpetuating the spread of the disease. The study then uses projections from mathematical models to suggest that RDTs need to be approximately 100 times more sensitive to detect these infectious individuals.

The work was conducted as part of the Diagnostics Modelling Consortium funded by the Bill and Melinda Gates Foundation and led by Imperial College London with significant input from the London School of Hygiene & Tropical Medicine and other partners.

Teun Bousema, a Senior Lecturer at the School and Radboud University Nijmegen, said “Currently used malaria diagnostics fail to detect many individuals who contribute to the spread of malaria. We performed hundreds of mosquito feeding assays to determine onward malaria transmission in relation to parasite densities. Our findings guide discussions on how better diagnostics can accelerate malaria elimination”.

Chris Drakeley, Professor of Immunology and Infection at the School, said “These papers show how integrating data collected in field studies with mathematical modeling can provide guidance on the necessary performance characteristics for diagnostics for malaria elimination”.

Whilst the data presented in these papers are important, the applicability to all malaria settings cannot be assessed without some element of field testing. Therefore, the challenge is to develop these more sensitive diagnostics and evaluate them in the places where they are needed.

Read a full press release on the Nature supplement on the Imperial College London website.

Publications:

 Wu L, van den Hoogen LL, Slater H, Walker PGT, Ghani AC et al: Comparison of diagnostics for the detection of asymptomatic Plasmodium falciparum infections to inform control and elimination strategies. Nature 528, S86-S93 (2015).

Slater H, Ross A, Lin Ouedraogo A, White LJ, Nguon C et al. Assessing the impact of next-generation rapid diagnostic tests on Plas­modium falciparum malaria elimination strategies. Nature 528, S94–S101 (2015).