Evidence Synthesis

Evidence synthesis is the process of gathering information from a wide range of disciplines and sources to better inform debates and decisions around a particular issue. They involve a methodical and comprehensive search of all of the research literature on a topic (including both published and unpublished work), focused by a specific research question. To avoid bias, evidence syntheses use objective, transparent and highly reproducible methods that are set out in advance. The most common example of this is systematic reviews.

When carried out well, they provide the most reliable evidence about the effects of interventions and policies used in health care, as well as identify any gaps in knowledge that may provide useful targets for future study.

We develop and use a range of evidence synthesis methods to bring evidence together in a robust and useful format. This enables healthcare professionals to deliver safe, effective care that is sustainable for the health system and makes better use of available evidence for more informed decisions reducing research waste. Evidence synthesis is a key component of the Health Technology Assessment process that LRiG carries out on behalf of the National Institute for Health and Care Excellence.

Expert Synthesis at Liverpool

Ruaraidh Hill leads the expert synthesis team, which focuses on research, teaching and learning related to evidence synthesis. Their research involves evidence synthesis of complex interventions and complex analyses, with reach that includes Institute, University and national collaborations across health, social care and education sectors. Their remit also includes capacity development across the University in evidence synthesis methods, offering support to PGR students carrying out projects, and a range of bespoke courses & workshops (see Resources tab for more).

Evidence Synthesis projects at LRiG

Safe and effective gradual reduction (tapering) of opioids in people with chronic non-cancer pain: systematic review of effects, barriers and facilitators and inequalities to inform service design in the NHS

Opioids have been used for pain management for centuries. However, current evidence suggests that the long-term use of opioid therapy is not effective for managing chronic non-cancer pain. People with chronic non-cancer pain may need to increase opioid dose to achieve pain relief which can lead to tolerance and dependency. Some people may also experience increased sensitivity to pain.

People with chronic non-cancer pain taking opioids long-term may need help to reduce their opioid use. This project aims to inform better practice, pathways and service design to support people with chronic pain to reduce their use of opioids and reduce inequalities. We are undertaking an evidence synthesis which includes systematic reviews of the quantitative and qualitative evidence, and the use of an emerging method - qualitative comparative analysis (QCA). The reviews will synthesise evidence on effectiveness, safety and acceptability of interventions to reduce opioid use; barriers to and facilitators of interventions; and inequalities in access to or benefiting from interventions.

Ruaraidh Hill. Rebecca Bresnahan. Rui Duarte. Juliet Hounsome. Michelle Maden.

Funding Details.

TAILOR medication synthesis - Optimising a whole-person-centred approach to stopping medicines in older people with multi-morbidity and polypharmacy

We contribute to the Tailor Medication Synthesis project, which aims to provide clinicians and patients with the information they need to make individual decisions about which medicines provide benefit and which they could stop. Doctors and patients alike have described feeling anxious about knowing when and how to stop long term medicines. Uncertainty about the risks involved can prevent people from making decisions. We conducted an extensive scoping review to complement a realist synthesis and patient and professional expert input.A report is being prepared and we will contribute to a stakeholder event and a learning package for professionals.

Ruaraidh Hill

Funding Details.

Health Effects of Liquid and Gaseous Fuel Use for Household Cooking, Heating, and Lighting

In 2014 the World Health Organisation (WHO) published the first WHO Guidelines for Indoor Air Quality: Household Fuel Combustion, which provide recommendations on emission rates for fuels and technologies to protect health and guidance on which fuels should not be used in the home. We are contributing to a review commissoned by the WHO that aims to address gaps in the evidence base regarding the health impacts from the use of liquid and gaseous fuels for cleaner household energy to replace solid fuels and kerosene. The findings of the review will form a database and be reported in peer-reviewed publications, to potentially be used to inform future air quality guidelines and policies supporting rapid transition to clean, efficient and safe household energy fuels and technologies.

Nigel Fleeman. Michelle Maden. Rui Duarte. Rebecca BresnahanKatherine Edwards. Angela Boland.

Funding Details.

For more examples see the Projects page.

Recent Evidence Synthesis publications

Spinal cord stimulation for the management of painful diabetic neuropathy: a systematic review and meta-analysis of individual patient and aggregate data

Spinal cord stimulation (SCS) has been suggested as a treatment option for patients with painful diabetic neuropathy (PDN). We conducted a systematic review and undertook a meta-analysis on individual patient data from randomised controlled trials (RCTs) to assess the effectiveness of SCS for the management of PDN. Our findings demonstrate that SCS is an effective therapeutic adjunct to best medical therapy in reducing pain intensity and improving health-related quality of life in patients with PDN.

Pain. 2021; 162 (11), 2635-2643. Rui Duarte. Sarah Nevitt. Michelle Maden.

Mindfulness-based cognitive therapy for prevention and time to depressive relapse: Systematic review and network meta-analysis

Mindfulness-based cognitive therapy (MBCT) is a pragmatic (but theoretically and experimentally derived) manualised treatment approach developed to address a common but specific clinical problem: frequent recurrence of depressive illness. In this review we carried out a network meta-analysis (NMA) to compare the long-term effectiveness of mindfulness-based cognitive therapy (MBCT) with available strategies for prevention and time to depressive relapse. Our  results  show  that  mindfulness-based  cogni-tive  therapy  has  advantages  when  compared  to  treatment as usual and placebo.

Acta Psychiatrica Scandinavica. 2021; 143, 6-21. Sarah Nevitt. Ruaraidh HillRui Duarte.

Are cleaner cooking solutions clean enough? A systematic review and meta-analysis of particulate and carbon monoxide concentrations and exposures

Globally, approximately 3 billion primarily cook using inefficient and poorly vented combustion devices, leading to unsafe levels of household air pollution (HAP) in and around the home. Such exposures contribute to nearly 4 million deaths annually. Characterizing the effectiveness of interventions for reducing HAP concentration and exposure is critical for informing policy and programmatic decision-making on which cooking solutions yield the greatest health benefits. This review synthesizes evidence of in-field measurements from four cleaner cooking technologies and three clean fuels, using field studies aimed at reducing HAP concentration and personal exposure to health damaging pollutants. Our results suggest that whilst clean cooking fuel interventions (LPG, electric) significantly reduce kitchen concentrations and personal exposure in household settings, stove stacking and background levels of ambient air pollution, have likely prevented most clean fuel interventions from approaching the World Health Organisation interim target level (WHO-IT1). This suggests that in order to maximize health gains, a wholistic approach jointly targeting ambient and HAP should befollowed in lower-and-middle income countries.

Environmental Research Letters. 2021; 16 (8), 083002. Nigel Fleeman. Rui Duarte. Michelle Maden.

For more examples see the Publications page.