The SLR Specification Manual
The Systematic Literature Review Specification Manual is the result of detailed expert consultation with the Methodology Task Force for the conduct of systematic literature reviews relevant to food, nutrition, physical activity and the aetiology of cancer worldwide.
The methodology in this manual, while drawing on the accumulated knowledge and success from other centres of excellence, has many important differences from previous methodologies, in particular in not employing a strict hierarchy of evidence in reviewing the literature.
An important aspect of an SLR is that all stages of searching, selection, assessment and analysis are pre-specified, objective and reproducible, openly documented and subject to peer review at critical stages.
The SLR manual provides full details of the approach taken and is designed to ensure not only a comprehensive and consistent approach to the analysis but also a common format for displaying the evidence. Science research teams collected and reviewed the literature based upon this methodology.
The SLR manual was tested by a process set up to evaluate whether two independent centres, in two continents, drew similar conclusions regarding the association of food, nutrition and physical activity and endometrial cancer, when provided with the same general instructions and with availability to similar resources (the SLR Specification Manual).
The findings of this process discussed in the Reproducibility Paper suggested that while the two SLRs showed some differences in terms of numbers of citations retrieved or decisions on relevance, the overall conclusions, particularly regarding which studies were most important and pooled risk estimates, were comparable.
This invaluable testing process enabled the SLR Specification Manual to be amended and improved, based on practical experience, prior to the other SLRs being undertaken.
Using the SLR Specification Manual
The first stage of the SLRs was a comprehensive search of the scientific literature and other sources catalogued on electronic databases, using all relevant keywords and terms. The papers identified were assessed for relevance using reproducible criteria. Study characteristics and results were extracted and recorded. Data from different studies were combined and analysed using meta-analysis when appropriate. Existing SLRs in the literature were also identified to ensure, as far as possible, that all relevant papers were included.
The SLRs include evidence published up to the end of 2005, and the Panel's conclusions are based on those SLRs. To ensure that the Panel's recommendations, which are derived from their conclusions and judgements, take into account developing evidence, a further review of studies published during 2006 was conducted. This review was more limited than the full SLRs, being confined to exposures that had been judged "convincing", "probable", "substantial effect on risk unlikely", and "limited-suggestive", based on the SLRs.
At this second review stage, no further meta-analyses were performed and a review of study quality was not included. For these reasons, the results of this 2006 review have been noted but have not been used to alter the Panel's judgements based on the full SLRs. A further process has been established for a continuous review of evidence published since 2006, after publication of this Report.
View and download a copy of the SLR Specification Manual.