The synthesis of scientific shreds of evidence: a critical appraisal on systematic review and meta-analysis methodology.

Synthesising results across studies to recognise the causes of variation in outcomes and to reach an overall understanding of a problem is a crucial part of the scientific method. Until in recent times, the results of scientific findings have been summarised in narrative reviews where the summary of transparent and objective results have become increasingly difficult. Systematic reviews and meta-analyses, conducted by subsequent strict protocols to guarantee reproducibility and decrease bias, have become more common in the synthesis of evidence.