Abstract / Summary
Abstract Objective This study assessed whether the 20-times (20x) washing procedure is a valid proxy for 36-month field ageing in insecticide-treated net (ITN) evaluation. Mosquito mortality and blood-feeding success were compared for three ITN products using both ageing methods. The assessment examined whether the methods produced similar outcome estimates and consistent non-inferiority conclusions relative to a first-in-class reference ITN. Results Estimated mosquito mortality was higher with 20×-washed nets than with 36-month field-aged nets. Feeding-success estimates differed less between ageing methods but showed greater uncertainty, with wider confidence intervals. Compared with field-aged nets, feeding success was slightly lower with 20×-washed Olyset ® Plus and Tsara ® Boost and slightly higher with Veeralin ® . Despite differences in point estimates, non-inferiority conclusions were consistent between ageing methods: Veeralin ® and Tsara ® Boost met the non-inferiority criterion relative to Olyset ® Plus for both outcomes. Thus, 20× washing did not reproduce the outcome estimates observed after 36 months of field ageing, although both methods produced the same non-inferiority conclusions. Studies including more ITN products, particularly those performing close to the non-inferiority margin, are needed to determine when conclusions from the two ageing methods may differ.