Conditional inference tree for soil-transmitted helminth infection with p-values adjusted for multiple comparisons.

<p>This is a sub-tree of the tree in <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002945#pntd-0002945-g002" target="_blank">Figure 2</a>. The p-values shown in each internal node are adjusted for multiple comparisons.</p

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

<div><p>Background</p><p>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.</p><p>Methodology</p><p>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.</p><p>Principal Findings</p><p>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.</p><p>Conclusions/Significance</p><p>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.</p></div

Conditional inference tree for soil-transmitted helminth infection, with infection by any helminth (<i>Ascaris lumbricoides, Trichuris trichiura,</i> or hookworm <i>spp</i>.) considered to be STH positive.

<p>Each internal node contains the name of the independent variable (IV) selected to partition the data, the p-value for the significance of the IV in the model, and the number of observations in the node. These nodes are numbered 1–11; the color of fill corresponds to the WASH characteristic of the IV and the border color represents how that characteristic was measured (e.g. at the school, home or pupil level). The branches emanating from each terminal node are labeled with the value of the IV used to partition the data. The square boxes represent terminal nodes and are numbered T1–T12 and contain the distribution of positive and negative cases at that terminal node. 1This variable started out as a 4-level ordinal variable for mother education but due to the optimal partition identified by the algorithm – “deceased’ vs. “no education”, “primary only”, and “secondary or more”– the variable ended up as indicator variables for mother deceased.</p

Summary of studies reporting on lymphedema morbidity management program.

<p>Summary of studies reporting on lymphedema morbidity management program.</p

Helminth incidence¹ by worm type (n = 1095).

1<p>Incidence because we are measuring reinfection following deworming.</p>2<p>By Kato-Katz.</p>3<p>Among positive cases.</p

Sample size calculations.

<p>Sample size calculations.</p

Meta-analysis examining the association between hygiene-based lymphedema management and the percentage of patients reporting at least one episode of ADLA during a specific time interval.

<p>Meta-analysis examining the association between hygiene-based lymphedema management and the percentage of patients reporting at least one episode of ADLA during a specific time interval.</p