Launch of the Parasite Clearance Estimator Online tool

WWARN Published Date

The emergence and spread of resistance to antimalarial drugs in South East Asia is threatening the effectiveness of existing drug treatments and our shared goal to work towards malaria elimination. As resistance spreads from Western Cambodia into neighbouring countries, research efforts are now focused upon the most widely used drugs known as artemisinin combination therapies (ACTs).

The parasite clearance rate - the speed at which parasite levels in the blood decline after treatment - is an important measure of antimalarial drug performance. It can be used to assess a patient’s response to treatment with artemisinin derivatives, evaluate new antimalarial drugs and analyse patient response rates in more severe cases of malaria and hyperparasitaemia. Researchers are focused on the urgent need to validate a molecular marker that can be used to identify the molecular basis of artemisinin resistance. Conventional in vitro assays continue to generate conflicting results while new assays will take time to be approved. For now, the clinical phenotype of slow parasite clearance remains the only way to reliably define artemisinin resistance.

This situation is further confounded by the absence of guidelines that define a consistent method of identifying resistance to artemisinin derivatives and has resulted in heterogeneous data which cannot be easily compared between populations and over time. While prolonged parasite clearance can be used as an important early warning signal of resistance, it can only be identified by comparing delayed clearance data with baseline parasite clearance rates. To respond to these important research needs, the WWARN team developed the Parasite Clearance Estimator (PCE) Online tool.

The Parasite Clearance Estimator provides a consistent, reliable and accurate approach to estimate malaria parasite clearance based on slope of the linear portion of the log-parasitaemia versus time relationship. Importantly, this method provides an indicator that is independent from the initial parasitaemia - a known bias when analysing parasite clearance time. The PCE approach can enable the detection of early changes in Plasmodium falciparum sensitivity to artemisinins and will support faster responses and, when necessary, guide changes to patient treatment approaches released by policy makers.

We encourage you to use PCE Online to analyse and cross-check your drug efficacy results. Once you’ve prepared and uploaded your data, a few clicks will produce a comprehensive report and multiple graphs which you can use and share to summarise your results.

To date, 95% of datasets analysed with PCE have then been shared with WWARN for pooled analysis. “If you’re able to share your data it will increase our collective understanding of parasite clearance rates, support improvements to the model and make an important contribution to our shared goal to fight resistance”, suggests Dr Kasia Stepniewska, WWARN Heads of Statistics.

PCE Online is simple to access and free - sharing your data is not required to use the tool.

Coming soon: The WWARN Molecular Scientific Group is currently working on core procedures for quantitative microscopy that are needed for parasite clearance estimations. These will include recommendations on how to prepare each step - including preparing smear samples, staining and reading - which together should help to increase the accuracy and quality of estimated parasite clearance rate results.

Login to WWARN or create an account to upload your data.

Contact us if you’d like support with using PCE Online or more information on the core procedures for quantitative microscopy needed to estimate parasite clearance rates.