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Study Design, Outcome Measurement, and Parameter Estimation for the Evaluation of an Ultraviolet Based Household Water Treatment and Safe Storage Intervention.

机译：用于评估基于紫外线的家庭水处理和安全存储干预措施的研究设计，结果测量和参数估计。

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In this dissertation, I present three chapters that further the evidence regarding HWTS strategies, trial methodologies, and outcome measures that are available to the HWTS sector. In Chapter 1, I report on the evaluation of a safe water program that promotes a novel ultraviolet-based HWTS strategy to rural Mexican households. Ultraviolet disinfection, while more expensive than the other HWTS technologies mentioned above, and requiring a nominal source of electricity, has the potential to reduce the barriers to adoption and sustained use: it is fast, it inactivates all classes of pathogens (bacteria, viruses, parasites), and does not change the taste or odor of the water. The study presented in this chapter represent the first health evaluation of an ultravioletbased HWTS strategy in a low- or middle-income country. The study design used for this evaluation, a randomized stepped wedge design, is also detailed; its advantages with respect to producing generalizable results are discussed. Specifically, the design allows an HWTS intervention to be rolled-out as it would have been under non-trial conditions, while maintaining the rigor of a randomized experimental design. The intention-to-treat (ITT) results from the trial show that while there were large improvements in drinking water quality (a 19 percentage point reduction [95% CI: -27%, -14%] in drinking water contamination, measured as the most probable number of Escherichia coli /100 ml [MPN EC]), there was not a significant reduction in the seven-day prevalence of self-reported diarrhea symptoms [Relative Risk (RR): 0.80 (95% CI: 0.51, 1.27)]. It is likely that a lower than expected prevalence in the control group reduced the power of the study to detect an effect of the intervention on diarrhea; however, the large impact of the intervention on drinking water contamination justifies expansion of the intervention to new regions. It is further concluded that future studies of potential health effects would be warranted, but in a larger study, or in an area with a higher burden of diarrheal illness.;In chapter 2, the effect of the intervention among households that "complied with the messages in the community intervention is explored, under the hypothesis that these households would have experienced greater reductions in drinking water contamination and diarrhea compared to the total population. The causal average complier effect (CACE) has been described for parallel arm trials, and is considered an estimate of treatment efficacy in effectiveness trials (i.e., a compliment to the ITT results reported in chapter 1). However, methods to estimate CACE in parallel arm trials require untestable assumptions. In this chapter a novel method to estimate the CACE parameter in a randomized stepped wedge trial is described. The primary insight from this chapter is that this method requires fewer assumptions than are necessary to estimate CACE in a parallel arm trial. To illustrate these methods, a definition of compliance is adopted, and effects of the intervention on household water quality and diarrhea are estimated among households that meet this definition. These stepped wedge CACE are compared to ITT results from the original trial and to CACE estimates from an instrumental variable (IV) estimator (a common method to estimate CACE in parallel arm trials). The stepped wedge CACE parameter estimated modest increases in reductions in drinking water contamination and diarrhea among complier households, compared to the ITT results from Chapter 1. In contrast, results from the IV estimator suggest a doubling in effect compared to the ITT estimates; however, it shown that violations of the assumptions necessary for IV estimation likely biased these results.;In the third and final chapter, the significance of measuring reductions in MPN EC (as a measure of water quality) in HWTS trials is considered. While most species of EC are not themselves pathogenic, they are excreted in large concentrations with human fecal material. Escherichia coli has therefore been a target indicator organism to test for the presence of fecal material and possible pathogen contamination in drinking water for over a century. For decades, in lieu of available methods to easily and cheaply test for EC in drinking water, there has been a reliance on surrogate indicators; the primary surrogate has been thermotolerant ("fecal") coliforms (FC). This chapter reports the results of a systematic review and meta-analysis that evaluates available evidence for a link between diarrhea and the presence of EC and FC in drinking water. The findings suggest that there is evidence to link diarrhea to EC (pooled RR: 1.54 [95% CI: 1.37, 1.74]) but not FC (pooled RR: 1.07 [95% CI: 0.79, 1.45]). It is concluded that this evidence supports the continued use of EC as an indicator organism to measure water quality in HWTS trials, and other field and research applications where an association with diarrhea is important; there is no evidence, however, to support the continued use of FC in these applications. The results from this review also serve to strengthen the findings and conclusion reported in chapter 1.
机译：在本文中，我将介绍三章，进一步介绍可用于HWTS部门的有关HWTS策略，试验方法和结果测量的证据。在第一章中，我报告了一项安全水计划的评估，该计划可为墨西哥农村家庭推广一种基于紫外线的新型HWTS策略。紫外线消毒虽然比上述其他HWTS技术昂贵，并且需要一定的名义电力供应，但它有可能减少采用和持续使用的障碍：它快速，能灭活所有种类的病原体（细菌，病毒，寄生虫），并且不会改变水的味道或气味。本章介绍的研究代表了在低收入或中等收入国家中对基于紫外线的HWTS策略的首次健康评估。还详细介绍了用于评估的研究设计，即随机阶梯楔形设计。讨论了其在产生可推广结果方面的优势。具体而言，该设计允许像在非试用条件下一样推出HWTS干预措施，同时保持随机实验设计的严格性。该试验的意向性处理（ITT）结果显示，尽管饮用水质量有了很大改善（饮用水污染降低了19个百分点[95％CI：-27％，-14％]，按大肠杆菌/ 100 ml [MPN EC]的最可能数量），自我报告的腹泻症状的7天患病率没有显着降低[相对风险（RR）：0.80（95％CI：0.51、1.27） ）]。对照组的患病率低于预期，可能会降低研究检测出干预措施对腹泻的效果的能力；但是，干预措施对饮用水污染的巨大影响证明了将干预措施扩展到新地区的合理性。进一步得出的结论是，有必要对潜在的健康影响进行进一步的研究，但是在更大的研究中或在腹泻病负担更大的地区。；在第二章中，“与在社区干预中传达的信息是基于这样的假设，即与总人口相比，这些家庭的饮用水污染和腹泻减少率将更大，平行安慰剂试验描述了因果平均依从效应（CACE），并被认为是有效性试验中对治疗效果的估计（即，对第1章中报告的ITT结果的补充）。但是，在平行臂试验中估计CACE的方法需要无法检验的假设。描述了随机阶梯楔形试验，本章的主要见解是该方法所需的假设少于必要的假设可以在平行试验中估算CACE。为了说明这些方法，采用了顺应性定义，并评估了达到该定义的家庭对家庭水质和腹泻的干预效果。将这些阶梯式楔形CACE与原始试验的ITT结果进行比较，并与工具变量（IV）估算器（在平行臂试验中估算CACE的常用方法）与CACE估算进行比较。与第1章的ITT结果相比，阶梯式楔形CACE参数估计的Complier家庭中饮用水污染和腹泻的减少有适度增加。相反，IV估计器的结果表明，与ITT估计相比，其效果成倍增长。但是，它表明违反了IV估计所必需的假设可能会使这些结果产生偏差。；在第三章和最后一章中，考虑了在HWTS试验中测量MPN EC减少量（作为水质的量度）的重要性。虽然大多数EC本身不是致病性的，但它们会通过人类粪便物质大量排泄。因此，大肠杆菌已经成为一种目标指示生物，用于测试粪便中是否存在以及饮用水中可能的病原菌污染。几十年来，代替了简便，廉价地检测饮用水中EC的可用方法，一直依赖替代指标。主要替代物是耐热（粪便）大肠菌群（FC）。本章报告了系统评价和荟萃分析的结果，该评价评估了腹泻与饮用水中EC和FC的存在之间的联系的可用证据。研究结果表明，有证据表明腹泻与EC（合并RR：1.54 [95％CI：1.37，1.74]）有关，而与FC无关（合并RR：1.07 [95％CI：0.79，1.45]）。结论是，该证据支持在HWTS试验中继续使用EC作为衡量水质的指标生物以及与腹泻相关的重要领域和其他研究应用；但是，没有证据支持在这些应用程序中继续使用FC。审查的结果也有助于加强第一章中报告的发现和结论。

著录项

  • 作者

    Gruber, Joshua Sean.;

  • 作者单位

    University of California, Berkeley.;

  • 授予单位 University of California, Berkeley.;
  • 学科 Epidemiology.;Engineering.;Public health.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 106 p.
  • 总页数 106
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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