Selecting and implementing overview methods: implications from five exemplar overviews

This is the final version of the article. Available from BioMed Central via the DOI in this record.Background Overviews of systematic reviews are an increasingly popular method of evidence synthesis; there is a lack of clear guidance for completing overviews and a number of methodological challenges. At the UK Cochrane Symposium 2016, methodological challenges of five overviews were explored. Using data from these five overviews, practical implications to support methodological decision making of authors writing protocols for future overviews are proposed. Methods Methods, and their justification, from the five exemplar overviews were tabulated and compared with areas of debate identified within current literature. Key methodological challenges and implications for development of overview protocols were generated and synthesised into a list, discussed and refined until there was consensus. Results Methodological features of three Cochrane overviews, one overview of diagnostic test accuracy and one mixed methods overview have been summarised. Methods of selection of reviews and data extraction were similar. Either the AMSTAR or ROBIS tool was used to assess quality of included reviews. The GRADE approach was most commonly used to assess quality of evidence within the reviews. Eight key methodological challenges were identified from the exemplar overviews. There was good agreement between our findings and emerging areas of debate within a recent published synthesis. Implications for development of protocols for future overviews were identified. Conclusions Overviews are a relatively new methodological innovation, and there are currently substantial variations in the methodological approaches used within different overviews. There are considerable methodological challenges for which optimal solutions are not necessarily yet known. Lessons learnt from five exemplar overviews highlight a number of methodological decisions which may be beneficial to consider during the development of an overview protocol.The overview conducted by Pollock [19] was supported by a project grant from the Chief Scientist Office of the Scottish Government. The overview conducted by McClurg [21] was supported by a project grant by the Physiotherapy Research Foundation. The overview by Hunt [22] was supported as part of doctoral programme funding by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care South West Peninsula (PenCLAHRC). The overview conducted by Estcourt [20] was supported by an NIHR Cochrane Programme Grant for the Safe and Appropriate Use of Blood Components. The overview conducted by Brunton [23] was commissioned by the Department of Health as part of an ongoing programme of work on health policy research synthesis. Alex Pollock is employed by the Nursing, Midwifery and Allied Health Professions (NMAHP) Research Unit, which is supported by the Chief Scientist Office of the Scottish Government. Pauline Campbell is supported by the Chief Nurses Office of the Scottish Government

The Effect of Natural Organic Matter on Mercury Methylation by Desulfobulbus propionicus 1pr3

Methylation of tracer and ambient mercury ((200)Hg and (202)Hg, respectively) equilibrated with four different natural organic matter (NOM) isolates was investigated in vivo using the Hg-methylating sulfate-reducing bacterium Desulfobulbus propionicus 1pr3. Desulfobulbus cultures grown fermentatively with environmentally representative concentrations of dissolved NOM isolates, Hg[II], and HS(-) were assayed for absolute methylmercury (MeHg) concentration and conversion of Hg(II) to MeHg relative to total unfiltered Hg(II). Results showed the (200)Hg tracer was methylated more efficiently in the presence of hydrophobic NOM isolates than in the presence of transphilic NOM, or in the absence of NOM. Different NOM isolates were associated with variable methylation efficiencies for either the (202)Hg tracer or ambient (200)Hg. One hydrophobic NOM, F1 HpoA derived from dissolved organic matter from the Florida Everglades, was equilibrated for different times with Hg tracer, which resulted in different methylation rates. A 5 day equilibration with F1 HpoA resulted in more MeHg production than either the 4 h or 30 day equilibration periods, suggesting a time dependence for NOM-enhanced Hg bioavailability for methylation

Use of grit supplements by waterbirds: an experimental assessment of strategies to reduce lead poisoning

The ingestion of spent Pb shot due to confusion with grit or inadvertently with food particles causes Pb poisoning in a large number of waterbirds, this being one of the main causes of mortality for some species. Lead ammunition for hunting is being progressively banned in more countries, while grit supplementation has been proposed as a management measure to reduce the ingestion of deposited Pb shot. Studies of grit selection with waterfowl in semi- captivity and in the wild were undertaken to evaluate preferences in the colour and geochemical composition of grit, whether it was available dry or in water, its position within the wetland and the relationship between grit ingestion and feeding behaviour. Grit ingestion was higher when food was included in the treatments. In the absence of food, red grit was taken in higher amounts than grey in semi-captivity but not in the wild. Siliceous grit was taken in a higher amount than calcareous when offered dry, but not in water. No differences in the amount of ingested grit were found among different positions within the wetland. The number of feeding attempts in plots supplemented with grit was higher than in those without grit, although the highest numbers of feeding birds were found in plots supplemented with food. Grit ingestion in waterfowl is intimately associated with feeding behaviour. To optimize the effectiveness of grit supplementa- tion to reduce the risk of Pb poisoning in waterfowl, calcareous and siliceous grit may be combined and applied in feeding sites or mixed with bait to attract birds.This work was supported by a project funded by the Consejería de Medio Ambiente, Junta de Andalucía. P. Acevedo is funded by a Juan de la Cierva research contract awarded by the Ministerio de Ciencia e Innovación—Fondo Social Europeo. This study was also funded by MICINN (under CGL2007-62797).Peer reviewe