Methods for surveillance of antimalarial drug efficacy
Routine monitoring of antimalarial drug efficacy is necessary for effective case management and early detection of resistance. WHO recommends that the efficacy of first and second-line antimalarial treatments be tested at least once every 24 months at all sentinel sites. When studies are conducted according to a standard protocol over a period of time, the data provides a key resource for informing national treatment policy.
Tools for monitoring antimalarial drug efficacy
WHO data collection for antimalarial therapeutic efficacy studies
In conjunction with the WHO standard protocol for monitoring antimalarial drug efficacy, WHO has developed a data collection form to standardize data entry and analysis of therapeutic efficacy study data. Separate versions are available for the 28-day and 42-day studies. The program can be used in areas of both high and low-to-moderate malaria transmission. Instructions are provided within the program, on the reference guide worksheet.
Data entry form - 28-day study
Data entry form - 42-day study
Parasite clearance estimator
In 2010, following the emergence of artemisinin resistance in South-East Asia, WHO defined suspected artemisinin resistance as an increase in parasite clearance time, as evidenced by > 10% of cases with parasites detectable on day 3 after treatment with an ACT. Studies of antimalarial drug efficacy have subsequently begun to monitor the proportion of patients with parasite clearance on day 3.
In addition, WHO has developed a parasite clearance estimator tool, which provides valuable information regarding the changes to the clearance rate. This excel based tool incorporates all phases of the parasite clearance curve: the initial lag phase, the slope, and the terminal tail phase. Each phase of the curve is considered to represent key biological processes, and may also be useful if the genetic heritability of artemisinin resistance is confirmed. This tool remains valid even when the parasite count is low.