WWARN launches new tool to monitor parasite clearance

Tracking the emergence and spread of resistance to artemisinin is challenging due to the complexity of measuring drug efficacy.  Parasite clearance (the rate at which parasitaemia declines) in response to artemisinin treatment has been the principal measure of drug efficacy to date and the only indicator of treatment response change. However clearance estimation is complicated by a lag phase, often seen before the parasite count falls, which needs to be identified by an observer, leading to possible inaccuracies and inconsistencies in the results.

To address this problem WWARN has launched the Parasite Clearance Estimator, a tool which identifies lag phase from the best fitting polynomial model and calculates clearance estimates adjusting for this lag phase.

The tool is the result of a six-month development project by the WWARN Clinical and Informatics teams.  Dr Kasia Stepniewska, WWARN Head of Statistics, explains: “Our aim was to provide the malaria community with a more accurate and consistent method of calculating parasite clearance estimates and the lag phase.  In the future we hope to use this tool to detect trends within responses to artemisinin therapies; the results have the potential to preserve ACTs as the first-line treatment for falciparum malaria throughout the world.”

Researchers with at least three positive parasite counts per patient over the period of clearance are invited to submit parasite clearance data and relevant study information through the WWARN Data Submission portal.  Until the tool is open access, WWARN will analyse submitted data offline. WWARN will return results to the data submitter, including an automated report summarising the study and the parasite clearance estimates, details of estimation and model fitting, and the estimates of parasite clearance and lag phase for each patient.

“The Parasite Clearance Estimator has been extensively tested thanks to the support of researchers who have already allowed us to analyse their data using the tool.  By making this available to all, we hope to support investigators comparing parasite clearance rate across time and regions.  Once we have expanded the database with more data sets we should be able to build a more comprehensive picture of antimalarial resistance”, added Dr Stepniewska.

To find out more visit Parasite Clearance Estimator on the WWARN website.  For more information contact pce@wwarn.org