Krølner et al. BMC Public Health 2012, 12:191 http://www.biomedcentral.com/1471-2458/12/191 Page 19 of 25 Table 6 Baseline characteristics of pupils at intervention-and control schools: key proximal outcomes Intervention sample (N = 1,121) Control sample (N = 1,035) Percentage (N) of pupils reporting the given characteristic N Percentage (N) of pupils Missing reporting the given characteristic N P-value from Missing chi-square test School availability of FV Having daily access to F in schools 50% (558) Having daily access to V in schools 26.9% (300) Home availability of FV Having daily access to F at home Having daily access to V at home Availability of FV at leisure time activities Always having access to F in at least one sports- or youth club* Always having access to V in at least one sports- or youth club* 46.8% (522) 53.8% (600) 25.6% (232) 13.0% (118) 6 6 6 6 8 8 46.6% (480) 27.4% (282) 43.4% (448) 55.8% (576) 30.0% (245) 12.0% (98) 4 4 2 2 9 9 p = 0.106 p = 0.816 p = 0.109 p = 0.365 p = 0.047 p = 0.503 Abbreviations: F = fruit, FV = fruit and vegetables, V = vegetables. *415 pupils who did not attend sports-or youth clubs were excluded from the analyses (Intervention sample: N = 207, control sample: N = 208) position, 4) to monitor intervention fidelity (adherence to implementation manuals), 5) to assess acceptability of the intervention, 6) to be able to decompose effects of each of the multiple components of intervention, and 7) to be able to provide recommendations on how to organise future school FV programmes [32,33]. Process evaluation questions were guided by Linnan & Steckler’s conceptual framework, Rogers’ diffusion of innovation theory, imple- mentation theory and other process evaluation studies [31,33,39,82,83]. Evaluation methods included teacher logbooks, computer tailoring track records, participant observations, focus group discussions with teachers and pupils, telephone interviews with local FV providers, and surveys among pupils, teachers, parents, and principals. Thorough description of the process evaluation is beyond the scope of this paper. Contamination issues Using data from 1st follow-up questionnaires among pupils and principals it will be measured 1) if any envir- onmental or educational activities have been conducted at control schools to promote FV consumption during the intervention period, 2) if the intervention in schools, sports-and youth clubs have spilled over to the control groups, 3) if any interfering events have influenced the implementation and effectiveness of the intervention e.g. schools closing down or change of principal or teachers. Economic evaluation Resources used for the intervention (training, production and implementation costs of intervention material and unit price and delivery expenses of FV, teacher prepara- tion time, extra cleaning because of FV programme etc.) have been systematically registered for cost-consequence analysis [84]. A societal perspective will be applied including analysis of the societal cost of nationwide roll- out of the Boost programme. These calculations may assist policy makers, principal and other stakeholders in evidence-based resource allocation by informing them about affordable, effective dietary interventions. Ethical considerations The Boost Project adheres to all Danish ethical standards and has been approved by the Danish data protection agency (J.nr. 2010-54-0974). When schools were invited to participate written information was sent to principals, par- ent boards and pupil councils at all schools explaining the implications of participating in the study. For focus groups and surveys, all respondents were informed that participa- tion was voluntary and anonymous and that all data would be handled confidentially. Parents could ask the research group to exclude their child’s survey responses from the database by ticking a box on the front page of the parent questionnaire. Furthermore, the parents could ask the research group by email or telephone not to collect the civil registration number of their child. This was collected by the project group to enable register-based follow-up evaluation of long-term effects. Discussion The Boost baseline results confirm the need for interven- tions as only 40% of the adolescents in this study reach the levels of FV intake recommended by WHO. Likewise, large proportions of pupils in the Boost study reported low access to fruit and especially vegetables in school, home and sports-and youth clubs at baseline. The novelty of the Boost intervention is that it is one of the first large-scale, school-based, multi-component, multi-level interventions to be implemented for a whole