Exploring changes in reported diarrhea among control group members in trials of water quality interventions Pubblico
Privette, Grayson Mitchell (2014)
Abstract
ABSTRACT
BACKGROUND Studies of the effect of water quality intervention on self-reported diarrheal disease have shown an apparent pattern of reduced levels of disease by members of the control group between baseline (or first surveillance point) and endline. If this change is statistically valid, it raises questions about the use of controls as a counterfactual to assess intervention effectiveness.
OBJECTIVE To determine whether and under what circumstances there are changes in reported diarrhea among control group members in trials of water quality interventions.
METHODS We compared levels of self-reported diarrhea at baseline (or first surveillance point) and endline from studies of water quality interventions. Studies were eligible for inclusion in the analysis if they were included in a 2014 systematic review of water quality interventions in low- and middle- income settings, the outcome was self-reported diarrhea and the required data was supplied by the study authors. Data was compiled on key study characteristics that could potentially explain changes in disease levels (study design, intervention type, length of follow up, etc.), presented descriptively, and analyzed using paired t tests.
RESULTS Of the 72 studies identified within the systematic review, 47 met the criteria for self-reported diarrhea as an outcome of interest. We were able to obtain data on beginning and end levels of diarrhea from 18 studies and included these in the analysis. Overall, there were no significant differences in the self-reported levels of diarrhea among control group members in water quality interventions from baseline (or first surveillance measure) to last surveillance measure. While differences were not statistically different, there was a consistent pattern of changes between beginning and end line outcomes, with 97% of the assessed relationships in this study showing a decline over time.
CONCLUSIONS Although no significant differences exist in reported diarrhea pre- and post-intervention, further research on this is warranted. A more comprehensive assessment of current water and sanitation literature may be able to elucidate the relationship suggested by these data of lower diarrheal disease reported among control group members in water and sanitation intervention trials.
Key words : water, sanitation, diarrhea, self-report, control group, paired t test
Table of Contents
TABLE OF CONTENTS
BACKGROUND & INTRODUCTION 1
METHODS 18
RESULTS 28
DISCUSSION 51
Conclusion & Recommendations 70
REFERENCES 73
APPENDIX 80
LIST OF TABLES
Table 1. Relevant Drinking-Water Intervention Characteristics for Paired T-Testing Analyses 27
Table 2. Selected Descriptive Characteristics 31
Table 3. Additional Selected Descriptive Characteristics 34
Table 4. Summary of Supplementary Data* 36
Table 5. Continuous Variable Characteristics, Water quality Interventions 38
Table 6. Results of Log-Transformed (log10) Paired T-Testing for Control Groups with Different Time
Points (n=18) 44
Table 7. Results of Stratified Paired T-Testing By Intervention Characteristic 48
Table 8. Results of Stratified Paired T-Testing By Low and High Levels of Continuous Variable
Characteristic 49
Table 9. Results of Stratified Paired T-Testing By Intervention Type 50
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