Julie Glanville

Associate Director, York Health Economics Consortium

Author of: What is a systematic review?

Julie is an active researcher in her field of information retrieval, a co-convenor of the Cochrane Information Retrieval Methods Group, a co-author of the Cochrane Handbook chapter on searching for evidence and a contributor to the SuRe Info resource for information specialists. She coordinates information and review services to York Health Economics Consortium (YHEC) customers.

Julie manages reviews ranging from rapid reviews to systematic reviews to inform submissions to reimbursement agencies such as NICE and also manages indirect and mixed treatment comparisons and coordinates YHEC’s training programme.

Before joining YHEC, Julie was Associate Director and Information Service Manager at the Centre for Reviews and Dissemination (CRD) at the University of York for fourteen years. In this role Julie managed information support for systematic reviews and technology assessments within CRD and to external customers, and managed CRD’s NHS Economic Evaluation Database. Julie has been involved in the production of hundreds of reviews in all topics. She was also a member of the Advisory Board of the UK Cochrane Centre.

Julie’s research interests are in search filter design and appraisal, and the efficient identification of research evidence for systematic reviews, economic evaluations and models and health technology assessments.

Summary: What is meta-analysis?

  • Meta-analysis is a set of statistical techniques for combining data from independent studies to produce a single estimate of effect
  • Meta-analysis is most often used within healthcare, but is also applied in other disciplines including psychology and the social sciences.
  • Within healthcare, meta-analysis is most often used to assess the clinical effectiveness of interventions; it does this by combining data from two or more studies (usually randomised controlled trials).
  • Meta-analysis of trials provides more precise estimates of treatment effect, by making use of all available data.
  • Meta-analysis is often part of the systematic review process, many systematic reviews include one or more meta-analyses.
  • The validity of any meta-analysis depends on the studies on which it is based.
  • Well-conducted meta-analyses aim for complete coverage of all relevant studies, look for the presence of heterogeneity among studies, and explore the robustness of the main findings using sensitivity analysis.

Summary: What is a systematic review?

  • Systematic reviews have increasingly become the ‘gold standard’ in reviewing. They aim to adopt a scientific approach to identifying and consolidating all the available evidence pertaining to a specific research question and to minimise bias.
  • Systematic reviews should be carried out according to a predefined protocol that sets out the scope of the systematic review and details of the methodology to be used throughout the review. Key components of a systematic review include:
    • Systematic and extensive searches to identify all the relevant published and unpublished literature
    • Study selection according to predefined eligibility criteria
    • Assessment of the risk of bias for included studies
    • Presentation of the findings in an independent and impartial manner
    • Discussion of the limitations of the evidence and of the review.
  • Systematic reviews can evaluate a range of evidence; qualitative, quantitative or both. Appropriate methods of synthesis should be used for different types of evidence.
  • The systematic review process has been developed to minimise bias and ensure transparency. Methods should be adequately documented so that they can be replicated.
  • When conducted well, systematic reviews should give us the best possible estimate of any true effect. An assessment of the methodological quality of reviews should highlight the limitations of a review.