Exploring the Relationship between Access to Water, Sanitation and Hygiene and Soil-Transmitted Helminth Infection: A Demonstration of Two Recursive Partitioning Tools

• Type of Material: Article
• Authors: Katherine Gass, Emory University; David G. Addiss, Emory University; Matthew Freeman, Emory University
• Language: English
• Date: 2014-06
• Publisher: Public Library of Science
• Publication Version: Final Published Version
• Copyright Statement: © 2014 Gass et al.
• Final Published Version (URL): http://www.plosntds.org/article/info%3Adoi%2F10.1371%2Fjournal.pntd.0002945
• Title of Journal or Parent Work: PLoS Neglected Tropical Diseases
• ISSN: 1935-2727
• Volume: 8
• Issue: 6
• Start Page: e2945
• End Page: e2945
• Grant/Funding Information: Data collection for this work was funded by the Bill & Melinda Gates Foundation and led by CARE USA.
• Research Categories: Health Sciences, Epidemiology; Health Sciences, Public Health

Abstract

Background: Soil-transmitted helminths (STH) – a class of parasites that affect billions of people – can be mitigated using mass drug administration, though reinfection following treatment occurs within a few months. Improvements to water, sanitation and hygiene (WASH) likely provide sustained benefit, but few rigorous studies have evaluated the specific WASH components most influential in reducing infection. There is a need for alternative analytic approaches to help identify, characterize and further refine the WASH components that are most important to STH reinfection. Traditional epidemiological approaches are not well-suited for assessing the complex and highly correlated relationships commonly seen in WASH. Methodology: We introduce two recursive partitioning approaches: classification and regression trees (C&RT) and conditional inference trees (CIT), which can be used to identify complex interactions between WASH indicators and identify sub-populations that may be susceptible to STH reinfection. We illustrate the advantages and disadvantages of these approaches utilizing school- and household-level WASH indicators gathered as part of a school-based randomized control trial in Kenya that measured STH reinfection of pupils 10 months following deworming treatment. Principal Findings: C&RT and CIT analyses resulted in strikingly different decision trees. C&RT may be the preferred approach if interest lies in using WASH indicators to classify individuals or communities as STH infected or uninfected, whereas CIT is most appropriate for identifying WASH indicators that may be causally associated with STH infection. Both tools are well-suited for identifying complex interactions among WASH indicators. Conclusions/Significance: C&RT and CIT are two analytic approaches that may offer valuable insight regarding the identification, selection and refinement of WASH indicators and their interactions with regards to STH control programs; however, they represent solutions to two distinct research questions and careful consideration should be made before deciding which approach is most appropriate. Author Summary: Soil-transmitted helminths (STH) are pervasive enteric parasites that lead to cognitive, nutritional and educational sequelae. Mass drug administration is employed to reduce morbidity, but reinfection occurs rapidly in the absence of changes to other environmental conditions, such as improvements to water, sanitation and hygiene (WASH). Since WASH behaviors and conditions are highly interrelated, typical epidemiological methods are limited. Few rigorous studies have assessed the impact of WASH components as they complement deworming and even fewer have sought to prioritize among the available indicators or identify complex interactions. In this paper we introduce two recursive partitioning approaches: classification and regression trees (C&RT) and conditional inference trees (CIT). We demonstrate these two tools using data from a school-based cluster-randomized trial conducted in Kenya. We discuss the advantages and disadvantages of each tool and give examples of how they may be used to improve STH control programs.