Abstract
BackgroundVariable exposure to causative agents of acute respiratory (RTI) or gastrointestinal tract infections (GTI) is a significant confounding factor in the analysis of the efficacy of interventions concerning these infections. We had an exceptional opportunity to reanalyze a previously published dataset from a trial assessing the effect of enhanced hand hygiene on the occurrence of RTI or GTI in adults, after adjustment for reported exposure and other covariates.MethodsTwenty-one working units (designated clusters) each including at least 50 office employees, totaling 1,270 persons, were randomized into two intervention arms (either using water-and-soap or alcohol-rub in hand cleansing), or in the control arm. Self-reported data was collected through weekly emails and included own symptoms of RTI or GTI, and exposures to other persons with similar symptoms. Differences in the weekly occurrences of RTI and GTI symptoms between the arms were analyzed using multilevel binary regression model with log link with personal and cluster specific random effects, self-reported exposure to homologous disease, randomization triplet, and seasonality as covariates in the Bayesian framework.ResultsOver the 16 months duration of the trial, 297 persons in the soap and water arm, 238 persons in the alcohol-based hand rub arm, and 230 controls sent reports. The arms were similar in age distribution and gender ratios. A temporally-associated reported exposure strongly increased the risk of both types of infection in all trial arms. Persons in the soap-and-water arm reported a significantly – about 24% lower weekly prevalence of GTI than the controls whether they had observed an exposure or not during the preceding week, while for RTI, this intervention reduced the prevalence only during weeks without a reported exposure. Alcohol-rub did not affect the symptom prevalence.ConclusionsWe conclude that while frequent and careful hand washing with soap and water partially protected office-working adults from GTI, the effect on RTI was only marginal in this study. Potential reasons for this difference include partially different transmission routes and a difference in the virus load. In this trial, frequent standardized hand rubbing with ethanol-based disinfectant did not reduce the weekly prevalence of either type of infections.Trial registrationClinicalTrials.gov Identifier: NCT00821509, 12 March 2009.
Highlights
Variable exposure to causative agents of acute respiratory (RTI) or gastrointestinal tract infections (GTI) is a significant confounding factor in the analysis of the efficacy of interventions concerning these infections
This divergence of the published results may be partly due to the multitude of difficult to control intervention-unrelated factors potentially affecting the outcome of the trial [13], which may result in a failure to identify all relevant factors that could be used in prerandomization stratification of the population in order to improve arm matching
We found that selfreported homologous exposures remarkably increased the relative risk of both self-reported respiratory tract infections (RTI) and GTI in this trial [15]
Summary
Variable exposure to causative agents of acute respiratory (RTI) or gastrointestinal tract infections (GTI) is a significant confounding factor in the analysis of the efficacy of interventions concerning these infections. The evidence for efficacy has been considered inconclusive [9, 10], and both positive effects [11] and lack of efficacy [12] have been reported in more recent studies This divergence of the published results may be partly due to the multitude of difficult to control intervention-unrelated factors potentially affecting the outcome of the trial [13], which may result in a failure to identify all relevant factors that could be used in prerandomization stratification of the population in order to improve arm matching. As discussed before [14], the performance of the trial was challenged by unexpected business-operational problems in some of the six committed corporations, unknown amount of “leakage” or contamination of the control clusters, and emergence of an outbreak of the A/H1N1v influenza pandemic in Finland The latter resulted in a well-publicized national campaign including recommendations for enhanced hand hygiene in order to minimize the disease burden due to the pandemic. Because of these undesired changes in the study setup, we initially made a simple global comparison of the infection rates of self-reported infection episodes between the arms before and during the pandemic and concluded, that frequent washing of hands with soap and water may reduce the rate of acute infections under the conditions used [14]
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