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Review 3: "Cost-effectiveness of Vector Control Strategies for Supplementing Mass Drug Administration for Eliminating Lymphatic Filariasis in India"

Reviewers have highlighted that this is an important study but raised major concerns related to the methods and data section, recommending the inclusion of robustness and sensitivity analysis.

Published onMar 12, 2024
Review 3: "Cost-effectiveness of Vector Control Strategies for Supplementing Mass Drug Administration for Eliminating Lymphatic Filariasis in India"
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key-enterThis Pub is a Review of
Cost-effectiveness of vector control strategies for supplementing mass drug administration for eliminating lymphatic filariasis in India
Cost-effectiveness of vector control strategies for supplementing mass drug administration for eliminating lymphatic filariasis in India
Description

Abstract Background/Methodology Despite progress using mass drug administration (MDA), lymphatic filariasis (LF) remains a major public health issue in India. Vector control (VC) is hypothesized as a potentially useful addition to MDA towards LF elimination. We conducted cost-effectiveness analysis of MDA alone and augmented by VC single (VCS) or integrated VC approaches (VCI). Data came from historical controls and a 3-arm cluster randomized trial of 36 villages at risk of LF transmission in Tamil Nadu, India. The arms were: MDA alone (the standard of care); VCS (MDA plus expanded polystyrene beads for covering the water surface in wells and cesspits to suppress the filariasis vector mosquito Culex quinquefasciatus), and VCI (VCS plus insecticidal pyrethroid impregnated curtains over windows, doors, and eaves). Economic costs in 2010 US$ combined government and community inputs from household to state levels. Outcomes were controlled microfilaria prevalence (MfP) and antigen prevalence (AgP) to conventional elimination targets (MfP<1% and AgP<2%) from 2010 to 2013, and disability adjusted life years (DALYs) averted.Principal Findings The estimated annual economic cost per resident was US$0.53 for MDA alone, US$1.02 for VCS, and US$1.83 for VCI. With MDA offered in all arms, all reduced LF prevalence substantially and significantly from 2010 to 2013. MDA proved highly cost effective at $112 per DALY, a very small (8%) share of India’s then per capita GDP. Progress towards elimination was comparable across all three study arms.Conclusions The well-functioning MDA was effective and very cost-effective for eliminating LF, leaving little scope for further improvement. Supplementary VC demonstrated no statistically significant additional benefit in this trial.Authors’ Summary Lymphatic filariasis (LF) is one of the twenty neglected tropical diseases (NTDs) that affect more than one billion people worldwide. As part of the effort toward global elimination of LF, the Indian State of Tamil Nadu government has implemented mass drug administration (MDA) repeatedly since 1996. Despite their efforts, LF had not yet been eliminated. Although vector control (VC) is proposed to augment regular MDA to help eliminate LF, little is known about the increased impact or costs. Our study compares the costs of MDA alone to the combination of MDA with alternative VC interventions. We calculated both program operating costs and costs to communities. We found MDA to be very cost-effective for eliminating LF. Against low levels of LF endemicity (≤10%), the study had limited ability to detect further improvements and found no significant incremental improvements from VC.

RR:C19 Evidence Scale rating by reviewer:

  • Reliable. The main study claims are generally justified by its methods and data. The results and conclusions are likely to be similar to the hypothetical ideal study. There are some minor caveats or limitations, but they would/do not change the major claims of the study. The study provides sufficient strength of evidence on its own that its main claims should be considered actionable, with some room for future revision.

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Review: The study’s objective is to evaluate the cost-effectiveness of MDA and augmenting MDA with vector control (VC) strategies to reduce lymphatic filariasis (LF) transmission. Data came from historical controls and a 3-arm cluster randomized trial of 36 villages at risk of LF transmission, which was conducted from 2010 to 2013 in Tamil Nadu, India. Using these data, the authors assessed these strategies' impact on disease prevalence and economic costs, providing a comprehensive analysis of their value in achieving local and global LF elimination goals. The findings reveal that the addition of VC methods to MDA did not lead to statistically significant improvements in LF transmission.

The key strengths of this study are its methodological rigor, transparency, and clarity. Specifically:

  1. The authors provided detailed break-down of costs, accounting for the lifetime of VC materials and their maintenance costs. They also clearly articulated their main findings, which is that MDA with VC strategies was dominated by MDA alone. This study, therefore, provides a nuanced understanding of how combined strategies are not always more effective and/or cost-effective, which can inform future policy decisions related to LF elimination in India and elsewhere.

  2. The study perspective is comprehensive. Authors performed the study from a community perspective. They not only collected personnel costs, including personnel salaries, but also non-personnel expenses such as treatment, transportation, and equipment costs (line 782). 

Our main critique of the paper is the the lack of sensitivity analysis/scenario analysis. This study may be lack of generalizability to the general Indian population as the authors have stated in their title (line 2), given the trial was performed single-centered with 12 villages in Tamil Nadu (line 149). This issue can be solved with multiple sensitivity analyses or scenario analyses, depicting how can the Incremental cost-effectiveness ratio (ICER) vary under different states in India. Please consider varying the salary/equipment costs with data other than Tamil Nadu to enhance the generalizability.

We also identified two minor weaknesses:

  1. It would be great if authors could add a table summarizing the trial information including number of participants in each arm, participant retention rate, and the quantity of equipment assigned to each arm during follow-ups.

  2. Regression results: In the linear regression result shown in table 6 (line 807), it appears that the model is not adjusted for potential confounders, and the R-squared values are low (0.31 and 0.28).

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