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Systematic Reviews By the 1980s the sheer volume of clinical trials already made it very difficult for doctors to keep up to date with all the results. Systematic reviews set a clearly formulated healthcare question. They use systematic and explicit methods to identify, select and critically appraise relevant randomised controlled trials. The data from the studies is collected and analysed to draw overall conclusions. Statistical methods (meta-analyses) may, or may not, be used to analyse and summarise the results of the included studies and to determine the size of the effect of the intervention, how likely one is to see that effect, that is, the observed variability of response. Cochrane reviews are published in The Cochrane Library ( www.thecochranelibrary.com) and are regularly updated. Barriers to use of evidence
- Healthcare studies are generally designed to assess the benefits rather than the harms of an intervention, which may be expected to occur considerably less frequently, especially in the relatively short designated time period of a randomised controlled trial
- The relevance of the defined outcomes for consumers, patients, carers and family OR policy makers
- Science tends to obscure the context of the data with the meaning of the measured numbers eg biochemical markers (creatinine levels, glycated haemoglobin) or physiological outcomes (arrhythmias, blood pressure, grip strength) compared with clinical (stroke, heart attack or death, ability to carry out daily tasks)
- It can take a decade or more to determine whether a drug actually works
- Marginal, highly vulnerable or disadvantaged people (for example with low levels of literacy or access to care, co-existing illnesses) are poorly represented in randomised studies; as are people at the two ends of the life span (children and the elderly).
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