The use of ‘PICO for synthesis’ and methods for synthesis without meta-analysis: protocol for a survey of current practice in systematic reviews of health interventions

INTRODUCTION: Systematic reviews involve synthesis of research to inform decision making by clinicians, consumers, policy makers and researchers. While guidance for synthesis often focuses on meta-analysis, synthesis begins with specifying the ’PICO for each synthesis’ (i.e. the criteria for deciding which populations, interventions, comparators and outcomes are eligible for each analysis). Synthesis may also involve the use of statistical methods other than meta-analysis (e.g. vote counting based on the direction of effect, presenting the range of effects, combining P values) augmented by visual display, tables and text-based summaries. This study examines these two aspects of synthesis. OBJECTIVES: To identify and describe current practice in systematic reviews of health interventions in relation to: (i) approaches to grouping and definition of PICO characteristics for synthesis; and (ii) methods of summary and synthesis when meta-analysis is not used. METHODS: We will randomly sample 100 systematic reviews of the quantitative effects of public health and health systems interventions published in 2018 and indexed in the Health Evidence and Health Systems Evidence databases. Two authors will independently screen citations for eligibility. Two authors will confirm eligibility based on full text, then extract data for 20% of reviews on the specification and use of PICO for synthesis, and the presentation and synthesis methods used (e.g. statistical synthesis methods, tabulation, visual displays, structured summary). The remaining reviews will be confirmed as eligible and data extracted by a single author. We will use descriptive statistics to summarise the specification of methods and their use in practice. We will compare how clearly the PICO for synthesis is specified in reviews that primarily use meta-analysis and those that do not. CONCLUSION: This study will provide an understanding of current practice in two important aspects of the synthesis process, enabling future research to test the feasibility and impact of different approaches

Critical elements of synthesis questions are incompletely reported: survey of systematic reviews of intervention effects

Objectives: To examine the characteristics of population, intervention and outcome groups and the extent to which they were completely reported for each synthesis in a sample of systematic reviews (SRs) of interventions. Study design and setting: We coded groups that were intended (or used) for comparisons in 100 randomly sampled SRs of public health and health systems interventions published in 2018 from the Health Evidence and Health Systems Evidence databases. Results: Authors commonly used population, intervention and outcome groups to structure comparisons, but these groups were often incompletely reported. For example, of 41 SRs that identified and/or used intervention groups for comparisons, 29 (71%) identified the groups in their methods description before reporting of the results (e.g., in the Background or Methods), 12 (29%) defined the groups in enough detail to replicate decisions about which included studies were eligible for each synthesis, 6 (15%) provided a rationale, and 24 (59%) stated that the groups would be used for comparisons. Sixteen (39%) SRs used intervention groups in their synthesis without any mention in the methods. Reporting for population, outcome and methodological groups was similarly incomplete. Conclusion: Complete reporting of the groups used for synthesis would improve transparency and replicability of reviews, and help ensure that the synthesis is not driven by what is reported in the included studies. Although concerted effort is needed to improve reporting, this should lead to more focused and useful reviews for decision-makers

Coating-free mirrors for high precision interferometric experiments

Thermal noise in mirror optical coatings may not only limit the sensitivity of future gravitational-wave detectors in their most sensitive frequency band but is also a major impediment for experiments that aim to reach the standard quantum limit or cool mechanical systems to their quantum ground state. We present the design and experimental characterization of a highly reflecting mirror without any optical coating. This coating-free mirror is based on total internal reflection and Brewster-angle coupling. In order to characterize its performance, the coating-free mirror was incorporated into a triangular ring cavity together with a high quality conventional mirror. The finesse of this cavity was measured using an amplitude transfer function to be about F≃4000. This finesse corresponds to a reflectivity of the coating-free mirror of about R≃99.89%. In addition, the dependence of the reflectivity on rotation was mapped out

Shape-induced force fields in optical trapping

Advances in optical tweezers, coupled with the proliferation of two-photon polymerization systems, mean that it is now becoming routine to fabricate and trap non-spherical particles. The shaping of both light beams and particles allows fine control over the flow of momentum from the optical to mechanical regimes. However, understanding and predicting the behaviour of such systems is highly complex in comparison with the traditional optically trapped microsphere. In this Article, we present a conceptually new and simple approach based on the nature of the optical force density. We illustrate the method through the design and fabrication of a shaped particle capable of acting as a passive force clamp, and we demonstrate its use as an optically trapped probe for imaging surface topography. Further applications of the design rules highlighted here may lead to new sensors for probing biomolecule mechanics, as well as to the development of optically actuated micromachines