Monitoring antimalarial drug efficacy

Therapeutic efficacy studies (TES)

Antimalarial drug efficacy is assessed through therapeutic efficacy studies (TES), the results of which are used by national malaria programmes as their primary reference to determine national treatment policies. TES are conducted in a controlled environment in which drug administration is supervised, the results of microscopic examinations of blood films are validated, and the origin and quality of the drugs are verified.

TES are prospective evaluations of patients’ clinical and parasitological responses to directly observed treatment for uncomplicated malaria. Studies at regular intervals at the same sites allow for the early detection of resistance and provide evidence for guiding national malaria treatment policy.

Therapeutic outcomes are assessed on the final day of the study (day 28, or day 42 for drugs with longer elimination half-lives). For infections appearing during follow-up, genotyping must be conducted to distinguish new infections from recrudescence.

While TES can help to predict the likelihood of antimalarial drug resistance, additional tools are needed to confirm its presence, such as in vitro tests, molecular analysis and measurements of drug concentrations. WHO has developed a standard protocol for monitoring therapeutic efficacy as well as tools for analysing TES results. The use of these standardized procedures facilitates the comparison of results within and across regions over time.

Network on monitoring antimalarial drug efficacy

WHO has supported the creation of several subregional networks for monitoring antimalarial drug efficacy and resistance. Through these networks, WHO is able to:

• provide updates on the global situation of antimalarial drug resistance;
• advise on study protocol implementation, microscopy procedures, data analysis and validation, and reporting support;
• provide updates on the most recent tools for monitoring drug efficacy and drug resistance.

The information on therapeutic efficacy generated by the networks and the experience acquired in the process are shared among countries in order to provide the best possible advice to ministries of health. The creation of networks allows for effective management of problems in border areas, where population movement is intense.

Reports of recent network meetings provide essential insights on monitoring of drug efficacy and resistance in the subregions.