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Systematic Reviews:

Systematic Reviews:. t heir contribution to knowledge. Morag Heirs. Research Fellow Centre for Reviews and Dissemination University of York. PhD student (NIHR funded) Health Sciences University of York. t: +44 (0)1904 321070 f: +44 (0)1904 321041 e: mkc500@york.ac.uk

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Systematic Reviews:

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  1. Systematic Reviews: their contribution to knowledge Morag Heirs

  2. Research Fellow Centre for Reviews and Dissemination University of York PhD student (NIHR funded) Health Sciences University of York t: +44 (0)1904 321070 f: +44 (0)1904 321041 e: mkc500@york.ac.uk www.york.ac.uk/inst/crd

  3. What is a systematic review • Systematic Review Review of a clearly formulated question that uses explicit methods to minimise bias in the location, selection, critical evaluation and synthesis of research evidence. (may or may not involve quantitative synthesis) • Meta-analysis Statistical techniques used to combine the results of two or more studies and obtain a pooled (combined) estimate of effect. (informative meta-analysis will usually also be a systematic review)

  4. Traditional reviews • ‘Unscientific’rarely pre-specify or make methods explicit • Usually subjective,opinions of individual • Often incomplete, filing cabinet or MEDLINE review • Difficult to make sense of conflicting or equivocal trials on qualitative reading alone

  5. Why we need systematic reviews Synthesis • Health care providers, researchers and policy makers are inundated with unmanageable amounts of information • Need systematic reviews to summarise existing information and provide data for rational decision making • Enable practitioners to keep up to date with evidence accumulating in field and to practice evidence-based medicine

  6. Why we need systematic reviews Totality of evidence • Evaluations and recommendations should be based on results of alltrials • not just published / well known trials that are likely to be biased towards positive (publication bias) • Results of any one trial should be interpreted in the context of all relevant evidence • consistency / inconsistency • generalisability

  7. Why we need systematic reviews Power and precision • Often the benefits that can be expected of a new intervention are moderate • These moderate benefits can be important clinically and in terms of public health • Often trials recruit too few patients to detect such differences with reliability

  8. Definitions and dilemmas • Systematic reviews • Are not restricted to including randomised controlled trials (RCTs) alone • Do not always include meta-analysis (but should always provide a synthesis) • Are a flexible and powerful methodology for answering a variety of questions

  9. Appraising systematic reviews • Adequate search • Defined inclusion criteria – appropriate choices to answer the question • Study selection/quality assessment/data extraction • Avoidance of bias and error • Synthesis (narrative, statistical, qualitative) taking into account quality of the primary studies

  10. Conclusions • Systematic reviews ≠ meta-analyses • Systematic reviews ≠ only looking at RCTs • Important to assess primary studies for risk of bias • Quality assess the systematic review itself • Systematic reviewing is a well established, adaptable methodology suitable for most topics and questions

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