WWARN presents tool to estimate parasite clearance at 7th EDCTP Forum
This week at the 7th EDCTP forum, Director of the Worldwide Antimalarial Resistance Network, Dr Philippe Guérin, presented on the subject; ‘Investigation of sampling designs for accurate estimation of parasite clearance in the context of artemisinin resistance.’
The emergence of Plasmodium falciparum resistance to antimalarial treatments can be measured by the reduced rate at which malaria parasite numbers are cleared from the patient’s system during treatment. Measurement of the rate at which the parasite is cleared remains a key way of determining the spread or emergence of artemisinin resistance to Plasmodium falciparum.
WWARN has developed a consistent and reliable method to estimate the rate of at which the malaria parasite is cleared from patients, a vital tool for assessing signs of change in antimalarial drug efficacy, especially response to artemisinins. With this freely available online tool, known as the Parasite Clearance Estimator, the rate at which the parasite is cleared from the patients’ system can be measured for individual patients and populations, and then compared between different study locations and times.
Figure 1: Presents the final linear model fitted to log-transformed data, once lag phase and tail are accounted for. The black dots in the linear portion of the curve are the values used to measure the parasite decline. Figure 2: Compares the estimated density function of slope half-lives (t½) between populations at different locations. This graph shows more evidence of extended half-life in Western Thailand and Cambodia studies.
The 7th EDCTP Forum was held between 30 June and 2 July 2014 in Berlin, Germany. The theme of the event was The Partnership journey: New Horizon for Better Health. At the Forum, Dr Guérin discussed how to optimise sample collection in order to accurately estimate parasite clearance when monitoring the spread or emergence of artemisinin resistance.
“The emergence of resistance to artemisinin therapies in Southeast Asia threatens the gains in malaria control made in the last decade,” says Dr Guérin. “Based on thousands of individual patients’ data shared by the research community, we have been in a position to develop and optimise a robust way to measure the parasite clearance for patients treated by an artemisinin derivative. Drug developers can also use this approach to evaluate a new compound.”
WWARN colleagues are now integrating this tool with several pooled analysis studies to provide reference parasite clearance estimates and investigate simpler, more practical sampling practices that still provide consistent and reliable results.
Other highlights from the EDCTP forum included a session on ‘Safety of artesunate-pyronaridine in the repetitive treatment of uncomplicated malaria in sub-Saharan Africa’ from WWARN’s Scientific Advisory Committee member, Dr Abdoulaye Djimdé - and ‘Effectiveness of seasonal malaria chemoprevention combined with community case management for malaria in southern Senegal: a cluster-randomised trial’ presented by partner Jean-Louis Ndiaye.
To request further information on the Parasite Clearance Estimator tool, share suggestions on how to modify or improve the tool, or to request a copy of the presentation from the 7th EDCTP Forum, please email pce@wwarn.org
Related articles
Flegg JA et al. Standardizing the measurement of parasite clearance in falciparum malaria: the parasite clearance estimator. Malaria Journal 2011. 10:339 doi:10.1186/1475-2875-10-339
Flegg JA et al. Optimal sampling designs for estimation of Plasmodium falciparum clearance rates in patients treated with artemisinin derivatives. Malaria Journal 2013. 12:411. doi: 10.1186/1475-2875-12-411.
Jamsen KM et al.A robust design for identification of the Parasite Clearance Estimator. Malaria Journal November 2013. 12:410. doi: 10.1186/1475-2875-12-410.