Environmental Engineering Reference
In-Depth Information
plans after study completion. It was not possible for the NGO to carry out the interven-
tion in all the communities at the same time, thus making randomization feasible and
acceptable to the three ethical review boards overseeing the study.
Sample size was calculated according to methods outlined by Hayes and Bennett
[16], assuming an IR in the control villages of fi ve episodes/child/year [17], and ac-
counting for clustering, the number of episodes, and the expected effect. We assumed
a coeffi cient of between-cluster variation ( k ) of similar studies, between 0.1 and 0.25
(as cited by Hayes and Bennett) and a minimum of 10 child-years of observation per
cluster [16]. We calculated that nine pairs of clusters were required to detect a differ-
ence of at least 33% in the IR between the control and intervention arms with 80%
power, k = 0.20 and an alpha level of 0.05. Anticipating a drop-out of at least one clus-
ter per arm and a loss of follow-up of individuals, the fi nal sample size was adjusted
to 11 pairs with 30 children per community cluster. We powered the study to detect a
33% reduction in diarrhea incidence after reviewing the evidence base for point-of-use
water treatment at the time of the study's inception in 2002 [18].
Implementation of the Intervention
The SODIS intervention was designed according to the published guidelines for na-
tional SODIS dissemination (http://www.sodis.ch/files/TrainingManual_sm.pdf).
Promotion activities were targeted at primary caregivers and all household members
(biweekly), whole communities (monthly), and primary schools (three times) by the
NGO as part of its regional community development program. Eleven communities
(262 households and 441 children) were randomized to the intervention; 11 communi-
ties (222 households, 378 children) served as a control group (Figure 1). For a period
of 15 month an intensive, standardized, and repeated interactive promotion of the SO-
DIS method was implemented in the intervention communities beginning 3 month
before the start of follow-up.
Within the intervention arm, participating households were supplied regularly with
clean, recycled PET bottles. The households were taught through demonstrations, role
plays, video, and other approaches to expose the water-fi lled bottles for at least 6 hr
to the sun. The NGO staff emphasized the importance and benefi ts of drinking only
treated water (especially for children), explained the germ--disease concept, and pro-
moted hygiene measures such as safe drinking water storage and hand washing as they
relate to the understanding of drinking water and the faecal--oral route of transmis-
sion of pathogens. During household visits the NGO staff encouraged all household
members to apply the method, answered questions, and assisted mothers and primary
caregivers to integrate the water treatment into daily life. The same intervention (in
terms of contents and messages) was supplied to the communities in the control arm
by the NGO-staff at the end of the study.
Outcome
The primary outcome was the IR of diarrhea among children <5 year, defined as num-
ber of diarrhea episodes per child per year obtained from daily assessment of indi-
vidual diarrhea occurrence. We applied the WHO definition for diarrhea of three or
 
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