Evidence from recent longitudinal studies supports the validity of this methodological approach [ 39].
As in any developing field of investigation, researchers must evaluate the validity and reliability of the methodological tools they employ.
Supporting the methodological validity of the Blanchard-Katz approach, relative employment growth and relative changes in the activity and unemployment rates tend to oscillate around constant averages.
To assess the methodological validity of the studies included in this review the following aspects were evaluated (according to a binary score presence/absence): randomization, allocation concealment, blinding and description of follow-up.
The methodological validity of the SRs was determined with the AMSTAR-R instrument, which has been found to give a reliable assessment of SRs [ 32].
The content validity of the VAS-IBS was the methodological judgement made by experts in the content area, and they completed a content validity index.
The assessment of the quality of evidence depended on the methodological validity of the SRs (AMSTAR-R score), together with the consistency of the results between the SRs (direction of effect and significance) [ 38, 39].
The methodological validity of the review is similarly problematic, mostly due to its lack of evidence concerning adequate allocation concealment, its blinding procedures, the similarity of intervention and control arms in terms of saturated fat intake and the predominance of industrially funded studies, as well as possible reporting bias.
In order to maintain the reliability and validity of the study, data and methodological triangulation were performed.
Yet, on most issues we found a wide consensus of experts across Europe, which may indicate the validity of the findings despite certain methodological shortcomings of the study.
