PLoS Medicine
http://www.plosmedicine.org/
(Accessed 25 July 2015)

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Guidelines and GuidanceIndividual Participant Data (IPD) Meta-analyses of Randomised Controlled Trials: Guidance on Their Use
Jayne F. Tierney, Claire Vale, Richard Riley, Catrin Tudur Smith, Lesley Stewart, Mike Clarke,
Maroeska Rovers
Published: July 21, 2015
DOI: 10.1371/journal.pmed.1001855
Summary Points
:: Systematic reviews are most commonly based on aggregate data extracted from publications or obtained from trial investigators.
:: Systematic reviews involving the central collection and analysis of individual participant data (IPD) usually are larger-scale, international, collaborative projects that can bring about substantial improvements to the quantity and quality of data, give greater scope in the analyses, and provide more detailed and robust results.
:: The process of collecting, checking, and analysing IPD is more complex than for aggregate data, and not all IPD meta-analyses are done to the same standard, making it difficult for researchers, clinicians, patients, policy makers, funders, and publishers to judge their quality.
:: Following our step-by-step guide will help reviewers and users of IPD meta-analyses to understand them better and recognise those that are well designed and conducted and so help ensure that policy, practice, and research are informed by robust evidence about the effects of interventions.