Assessing the variability in experimental hut trials evaluating insecticide-treated nets against malaria vectors

Challenger, Joseph D.; Nash, Rebecca K.; Ngufor, Corine; Sanou, Antoine; Toé, Hyacinthe K.; Moore, Sarah; Tungu, Patrick; Rowland, Mark; Foster, Geraldine M.; N’Guessan, Raphaël; Sherrard-Smith, Ellie; Churcher, Thomas S

doi:10.1016/j.crpvbd.2023.100115

Cited by 8 publications

(9 citation statements)

References 23 publications

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“…In this approach, appropriate method validation is paramount for building confidence in the method results and providing solid scientific evidence for its, and, by extension, the product’s, performance [ 20 , 22 , 23 , 25 , 64 ]. Ignoring the various sources of variability and/or not properly assessing bioassay and semi-field test precision could lead to misleading conclusions that inform future decisions [ 12 , 61 ]. Therefore, a standardized approach to method validation that can be employed by manufacturers to ensure that the bioassays, tests and equipment used to evaluate vector control products are fit for purpose and reliable is necessary.…”

Section: Discussionmentioning

confidence: 99%

“…Data from feasibility studies are used in a formal power calculation to determine the sample size for internal validation. This can be achieved by using standard formulas for sample size estimation or simulation studies for complex designs involving multiple varying factors and testing schema [ 59 – 61 ]. The predefined effect size for the primary endpoint of interest together with the SD/variability estimated from the feasibility experiments should be used to estimate the sample size.…”

Section: Text Box 1 Terminologymentioning

confidence: 99%

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A bioassay method validation framework for laboratory and semi-field tests used to evaluate vector control tools

Matope,

Lees,

Spiers

et al. 2023

Malar J

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Vector control interventions play a fundamental role in the control and elimination of vector-borne diseases. The evaluation of vector control products relies on bioassays, laboratory and semi-field tests using live insects to assess the product’s effectiveness. Bioassay method development requires a rigorous validation process to ensure that relevant methods are used to capture appropriate entomological endpoints which accurately and precisely describe likely efficacy against disease vectors as well as product characteristics within the manufacturing tolerance ranges for insecticide content specified by the World Health Organization. Currently, there are no standardized guidelines for bioassay method validation in vector control. This report presents a framework for bioassay validation that draws on accepted validation processes from the chemical and healthcare fields and which can be applied for evaluating bioassays and semi-field tests in vector control. The validation process has been categorized into four stages: preliminary development; feasibility experiments; internal validation, and external validation. A properly validated method combined with an appropriate experimental design and data analyses that account for both the variability of the method and the product is needed to generate reliable estimates of product efficacy to ensure that at-risk communities have timely access to safe and reliable vector control products.

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Section: Discussionmentioning

confidence: 99%

Section: Text Box 1 Terminologymentioning

confidence: 99%

A bioassay method validation framework for laboratory and semi-field tests used to evaluate vector control tools

Matope,

Lees,

Spiers

et al. 2023

Malar J

Self Cite

View full text Add to dashboard Cite

show abstract

“…In this approach, appropriate method validation is paramount for building con dence in the method results and providing solid scienti c evidence for its, and, by extension, the product's, performance [17,19,20,22,44]. Ignoring the various sources of variability and/or not properly assessing bioassay and semi-eld test precision could lead to misleading conclusions that inform future decisions [12,41]. Therefore, a standardised approach to method validation that can be employed by manufacturers to ensure that the bioassays, tests and equipment used to evaluate vector control products are t for purpose and reliable is necessary.…”

Section: Discussionmentioning

confidence: 99%

“…Determining appropriate sample size and study design Data from feasibility studies are used in a formal power calculation to determine the sample size for internal validation. This can be achieved by using standard formulas for sample size estimation or simulation studies for complex designs involving multiple varying factors and testing schema [39][40][41]. The prede ned effect size for the primary endpoint of interest together with the SD/variability estimated from the feasibility experiments should be used to estimate the sample size.…”

Section: Internal Validationmentioning

confidence: 99%

A bioassay method validation framework for laboratory and semi-field tests used to evaluate vector control tools

Matope

Lees

Spiers

et al. 2023

Preprint

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Vector control interventions play a fundamental role in the control and elimination of vector-borne diseases. The evaluation of vector control products relies on bioassays, laboratory and semi-field tests that use live insects, to assess the product’s effectiveness. Bioassay method development requires a rigorous validation process to ensure that relevant methods are used that capture appropriate entomological endpoints which accurately and precisely describe likely efficacy against disease vectors as well as product characteristics within the manufacturing tolerance ranges for insecticide content specified by the World Health Organisation. Currently, there are no standardised guidelines for bioassay method validation in vector control. This report presents a framework for bioassay validation that draws on accepted validation processes from the chemical and healthcare fields and which can be applied for evaluating bioassays and semi-field tests in vector control. The validation process has been categorised into four stages: preliminary development; feasibility experiments; internal validation, and external validation. A properly validated method combined with an appropriate experimental design and data analyses that account for both the variability of the method and the product is needed to generate reliable estimates of product efficacy to ensure that at-risk communities have timely access to safe and reliable vector control products.

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“…For each experimental hut trial and at each timepoint, data on the number of mosquitoes per night and the magnitude of the different random effects (huts, sleepers, nights and observational error) will be reviewed after the first round of 9 or 13 weeks and power calculations conducted by simulation using previously described methods [ 33 ]. Power analysis will determine whether the hut trial has a desired 80% power to detect superiority in mosquito killing of any new unused dual AI ITN over the new unused pyrethroid-only net, assuming a true underlying extra mortality from the dual AI net of 40%.…”

Section: Methodsmentioning

confidence: 99%

Evaluating the attrition, fabric integrity and insecticidal durability of two dual active ingredient nets (Interceptor® G2 and Royal® Guard): methodology for a prospective study embedded in a cluster randomized controlled trial in Benin

Ngufor,

Fongnikin,

Fagbohoun

et al. 2023

Malar J

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Background Following the World Health Organization (WHO) endorsement of dual active ingredient (AI) nets, an increased uptake of pyrethroid-chlorfenapyr and pyrethroid-pyriproxyfen nets is expected. Studies evaluating their physical and insecticidal durability are essential for making programmatic and procurement decisions. This paper describes the methodology for a prospective study to evaluate the attrition, fabric integrity, insecticidal durability of Interceptor® G2 (alpha-cypermethrin-chlorfenapyr) and Royal Guard® (alpha-cypermethrin-pyriproxyfen), compared to Interceptor® (alpha-cypermethrin), embedded in a 3-arm cluster randomized controlled trial (cRCT) in the Zou Department of Benin. Methods Ten clusters randomly selected from each arm of the cRCT will be used for the study. A total of 750 ITNs per type will be followed in 5 study clusters per arm to assess ITN attrition and fabric integrity at 6-, 12-, 24- and 36-months post distribution, using standard WHO procedures. A second cohort of 1800 nets per type will be withdrawn every 6 months from all 10 clusters per arm and assessed for chemical content and biological activity in laboratory bioassays at each time point. Alpha-cypermethrin bioefficacy in Interceptor® and Royal Guard® will be monitored in WHO cone bioassays and tunnel tests using the susceptible Anopheles gambiae Kisumu strain. The bioefficacy of the non-pyrethroid insecticides (chlorfenapyr in Interceptor® G2 and pyriproxyfen in Royal Guard®) will be monitored using the pyrethroid-resistant Anopheles coluzzii Akron strain. Chlorfenapyr activity will be assessed in tunnel tests while pyriproxyfen activity will be assessed in cone bioassays in terms of the reduction in fertility of blood-fed survivors observed by dissecting mosquito ovaries. Nets withdrawn at 12, 24 and 36 months will be tested in experimental hut trials within the cRCT study area against wild free-flying pyrethroid resistant An. gambiae sensu lato to investigate their superiority to Interceptor® and to compare them to ITNs washed 20 times for experimental hut evaluation studies. Mechanistic models will also be used to investigate whether entomological outcomes with each dual ITN type in experimental hut trials can predict their epidemiological performance in the cRCT. Conclusion This study will provide information on the durability of two dual AI nets (Interceptor® G2 and Royal Guard®) in Benin and will help identify suitable methods for monitoring the durability of their insecticidal activity under operational conditions. The modelling component will determine the capacity of experimental hut trials to predict the epidemiological performance of dual AI nets across their lifespan.

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Assessing the variability in experimental hut trials evaluating insecticide-treated nets against malaria vectors

Cited by 8 publications

References 23 publications

A bioassay method validation framework for laboratory and semi-field tests used to evaluate vector control tools

A bioassay method validation framework for laboratory and semi-field tests used to evaluate vector control tools

A bioassay method validation framework for laboratory and semi-field tests used to evaluate vector control tools

Evaluating the attrition, fabric integrity and insecticidal durability of two dual active ingredient nets (Interceptor® G2 and Royal® Guard): methodology for a prospective study embedded in a cluster randomized controlled trial in Benin

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