In the third synthesis we used the results of our qualitative synthesis to combine the findings from the controlled trials and qualitative studies. We then devised a matrix that juxtaposed the barriers, facilitators, and implied recommendations against the actual interventions that had been implemented and evaluated. Since we could not know the outcome of the qualitative synthesis in advance, we had to go back to the original interventions evaluated in the trials to identify those that built on the barriers and facilitators suggested by the children. This comparative analysis was guided by three questions:
- Which interventions match recommendations derived from children's views and experiences?
- Which recommendations have yet to be tried in soundly evaluated interventions?
- Do those interventions that match recommendations show bigger effect sizes or explain heterogeneity?
The shows an example from the matrix. We used the good quality trials to assess whether the evidence of effectiveness supported or contradicted the children's views and to identify gaps in the evidence. The interventions that had not been evaluated well but were identified as building on a potential facilitator were recommended for more rigorous evaluation.
Example of the synthesis matrix
For the recommendation that fruit and vegetables should not be promoted in the same way, we found no sound trials, so we identified a research gap. We found five good quality trials relevant to the second recommendation—reducing the emphasis on health messages. Two of these provided results on the same outcome, so we were able to conduct a statistical subgroup analysis dividing the studies into those that emphasised health messages and those that did not. (Since the original meta-analysis in synthesis 1 suggested that interventions targeting physical activity as well as healthy eating were qualitatively different from those that did not, the subgroup analysis excluded the interventions with a physical activity component.)
Qualitative studies improve understanding of the views of the target group of an intervention
Uncertainty exists about how to include qualitative research within systematic reviews
A three stage method is described to integrate qualitative studies with controlled trials in one systematic review
Integration of the two types of studies can identify ways to improve interventions and their implementation
shows data from the trials in this subgroup analysis. The only two studies to increase vegetable consumption by more than 0.4 portion a day were the two that had little or no emphasis on health messages. We found that highly significant heterogeneity was explained by this subdivision.13
As with any exploration of heterogeneity, this was an exercise in hypothesis generation. Since we were dealing with small numbers of studies, our conclusions had to be cautious.
Increase in consumption of fruit and vegetables in trials with data on health emphasis