Why the Meta Analysis is Original and How does it Provide the Best Evidence?

Abstract

Meta-analyses play a fundamental role in evidence-based healthcare. Compared to other study designs (such as randomized controlled trials or cohort studies), the meta-analysis comes in at the top of the ‘levels of evidence’ pyramid in evidence-based healthcare. This is a pyramid which enables us to weigh up the different levels of evidence available to us. Meta-analysis contributes to many aspects of different research, for example: 1) Meta analysis is not a method as the combination of the studies like as review study. It produces new knowledge instead of summarizing what is already known, 2) Meta-analysis is considered as an original article. Because it covers the original statistical methods. Therefore the results of Meta-analysis also are original, 3) It is the best evidence method, 4) It develops new scientific tools, 5) It provides guidelines for solving problems by using big sample size, 6) Combines the results of studies that are reverse and also puts the end point for these contrasting results, 7) Increases the statistical power by combining different studies, 8) It leads a higher statistical power and more robust point estimate than is possible from the measure derived from any individual study, 9) It produces a new weighted average of the included study results, 10) It is limited to the quality of studies that are included, 11) To provide a more precise and new estimate of the overall treatment effects. There are two main models in meta-analysis: the fixed effects model and the random effects model. To determine which model to use, whether the model’s prerequisites were met by the characteristics of the research studies included in the meta-analysis were considered. Because the source of heterogeneity is often unexplained therefore if the source of heterogeneity can not be explained, in this case it is recommended to use a random effects model. At the result, if there is no heterogeneity, the fixed effects model is used. If there is heterogeneity, random effects model should be preferred. As a result, we can say that meta-analysis will be encountered in research for future and it is a significant original method with many benefits.