The gap between research and practice or policy is often described as a problem. To identify new barriers of and facilitators to the use of evidence by policymakers, and assess the state of research in this area, we updated a systematic review.

Summary Mixed methods research is the use of quantitative and qualitative methods in a single study or series of studies. It is an emergent methodology which is increasingly used by health researchers, especially within health services research. There is a growing literature on the theory, design and critical appraisal of mixed methods research. However, there are few papers that summarize this methodological approach for health practitioners who wish to conduct or critically engage with mixed methods studies. The objective of this paper is to provide an accessible introduction to mixed methods for clinicians and researchers unfamiliar with this approach. We present a synthesis of key methodological literature on mixed methods research, with examples from our own work and that of others, to illustrate the practical applications of this approach within health research. We summarize definitions of mixed methods research, the value of this approach, key aspects of study design and analysis, and discuss the potential challenges of combining quantitative and qualitative methods and data. One of the key challenges within mixed methods research is the successful integration of quantitative and qualitative data during analysis and interpretation. However, the integration of different types of data can generate insights into a research question, resulting in enriched understanding of complex health research problems.

There are high levels of concern about childhood obesity, with obese children being at higher risk of poorer health both in the short and longer terms. Children's attitudes to, and beliefs about, their bodies have also raised concern. Children themselves have a stake in this debate; their perspectives on this issue can inform the ways in which interventions aim to work.

Objectives To determine the clinical effectiveness of screening tests for physical abuse in children attending accident and emergency (A&E) departments in the UK. Data sources Searches were limited to studies published after 1974 and were carried out from August 2004 to October 2006 using the following methods: searching electronic databases, searching the publications catalogue of the NSPCC, scanning reference lists, hand-searching journals, searching the internet, approaching professional contacts for unpublished data, and searching in three key journals. Review methods A simple decision-analytic model was used to integrate the findings of nine systematic reviews regarding the incidence of physical abuse, the characteristics of children attending A&E, and the performance of screening tests for physical abuse. Results A total of 66 studies, including 11 unpublished studies, were included in the nine systematic reviews. Overall the quality was poor. There was consistent evidence that physical abuse affects about 1 in 11 children in the UK each year. The proportion of abused children requiring medical attention is small but poorly quantified. Approximately 1% of all attendances of injured children at A&E are for physical abuse. There was clear evidence that physically abused children attending A&E are missed, but the performance of the clinical screening assessment was poorly quantified. There was no evidence that any test was highly predictive of physical abuse. Among severely injured children admitted to hospital, those under 1 year were more likely to be abused than older children. However, evidence that young age was a risk factor for abuse among all injured children attending A&E was inconsistent. There was weak evidence that a community liaison nurse improved the performance of the screening assessment in A&E, and it was estimated that combining a nurse with the standard screen would result in referral to social services of about half of the abused children attending A&E. However, given the poor quality of the data, this is highly uncertain. The addition of screening protocols to the clinical screening assessment offered marginal benefits, and additional false-positive referrals exceeded additional abused children detected. The benefits of protocols declined as the accuracy of the clinical screening assessment improved. The most effective protocol was to refer all injured infants and children who were social work active. Conclusions Improving clinical screening assessment is likely to be more useful than protocols in improving the detection of physically abused children attending A&E. Further improvements might be achieved by following up children referred to paediatricians for suspected abuse who fail to reach the high level of certainty required to justify referral to social services. Many professionals voiced a need for access to experienced social services advice that is not under pressure to minimise referrals to an overloaded service, and consideration might be given to making such advice centrally available.