Linking quantitative microbial risk assessment and epidemiological data: informing safe drinking water trials in...

Area of Science:

• Environmental Health Engineering
• Infectious Disease Epidemiology
• Risk Assessment

Background:

• Household water treatment (HWT) intervention trials are crucial for evaluating diarrheal disease reduction in developing nations.
• Policy decisions based on HWT trial data require addressing generalizability and systematic biases in study design and conduct.
• Quantitative Microbial Risk Assessment (QMRA) offers a framework to evaluate water safety and health impacts.

Purpose of the Study:

• To analyze a randomized controlled trial (RCT) of the LifeStraw Family Filter using QMRA to assess water safety and health.
• To illustrate how QMRA can address generalizability and bias issues in HWT intervention trials.
• To quantify the impact of compliance and epidemiological biases on HWT efficacy.

Main Methods:

• Analyzed a published RCT of the LifeStraw Family Filter in the Congo.
• Developed a QMRA model accounting for biases: incomplete compliance, placebo antimicrobial activity, and recall bias.
• Measured effectiveness using the longitudinal prevalence ratio (LPR) of reported diarrhea.

Main Results:

• The original RCT reported an LPR of 0.84.
• The QMRA model predicted LPRs ranging from 0.50 (high compliance) to 0.86 (low compliance), assuming a perfect placebo.
• Model calibration estimated pathogen concentrations (E. coli, Giardia, rotavirus) consistent with trial data.

Conclusions:

• QMRA effectively demonstrates the critical role of user compliance in HWT efficacy.
• Pathogen data from source waters are essential for accurate HWT effectiveness assessments.
• QMRA aids in quantifying biases and generalizing HWT trial findings to diverse contexts.