A demonstration of using formal consensus methods within guideline development; a case study

BACKGROUND

Recommendations within guidelines are developed by synthesising the best available evidence; when limited evidence is identified recommendations are generally based on informal consensus. However, there are potential biases in group decision making, and formal consensus methods may help reduce these.

METHODS

We conducted a case study using formal consensus, to develop one set of recommendations within the Neonatal Parenteral Nutrition guideline being produced for the National Institute for Health and Care Excellence. Statements were generated through identification of published guidelines on several topics relating to neonatal parenteral nutrition. Ten high quality guidelines were included, and 28 statements were generated; these statements were rated by the committee via two rounds of voting. The statements which resulted in agreement were then used to develop the recommendations.

RESULTS

The approach was systematic and provided transparency. Additionally, a number of lessons were learnt; including the value of selecting the appropriate topic, giving adequate time to the process, and ensuring methodologies are understood by the committee for their value and relevance.

CONCLUSION

Formal consensus is a valuable option for use within guideline development when specific criteria are met. The approach provides transparent methodology, ensuring clarity on how recommendations are developed.

Enhanced Nonlinear Optical Effect in Hybrid Liquid Crystal Cells Based on Photonic Crystal

Nonlinear-optical response of photorefractive hybrid liquid crystal (LC) cells has been studied by means of dynamic holographic technique in two-wave mixing arrangement. The LC cells include nonuniform silicon substrates comprising a micrometer-range photonic crystal. A thin LC layer is set between silicon substrate and a flat glass substrate covered by a transparent (ITO) electrode. A dynamic diffraction grating was induced in the LC volume by the two-wave mixing of laser beams with simultaneous application of DC electric field to the cell. Theoretical model of Raman-Nath self-diffraction was developed. This model allows for calculation of nonlinear optical characteristics in thin samples on the base of two-wave mixing experimental data, and with taking into account light losses on absorption and/or scattering. The hybrid LC cells demonstrate strong nonlinear optical effect, prospective for many applications in electro-optical microsystems, such as SLMs, as well as in multi-channel systems.