ADVANTAGES AND DISADVANTAGES OF THE METAANALYSIS APPROACH

Advantages of meta-analysis Literature reviews have traditionally been largely narrative, Meta-analysis now offers the opportunity to critic ally evaluate and statistically combine results of comparable studies or trials. Its major purposes are to increase the numbers of observati ons and the statistical power, and to improve the estimates of the eff ect size of an intervention or an association. Methods There is, as ye t, no unanimously accepted strategy for performing a meta-analysis but researchers agree that each meta-analysis should be conducted like a scientific experiment and begin with a protocol, which clearly states its aim and methodology, Meta-analysts disagree on the criteria for in clusion or exclusion of primary studies, with relation to publication status, comparability and required scientific quality, but sensitivity analyses make it possible to assess the impact of various selection c riteria on the results, Several statistical methods have been develope d to analyse data extracted from the literature; more recently, meta-a nalyses have also been performed on individual subject data. Conclusio ns Meta-analysis is superior to narrative reports for systematic revie ws of the literature, but its quantitative results should be interpret ed with caution even when the analysis is performed according to rigor ous rules.