ABSTRACT
2Meta-analysis can be defined as a systematic statistical method for analyzing and synthesizing results from independent studies, taking into account all pertinent information. Readers of narrative studies face problems such as lack of detailed description, the process that led to the review, and hence the readers cannot replicate and verify the results and conclusions of the review. Most effective mechanism for systematic review is to reduce bias and increase precision, by including maximum possible number of relevant individual studies and providing a detailed description of their strengths and limitations. Vote counting is clearly unsound, since it ignores sample size, effect size, and research design. Meta-analysis is trying to answer four basic questions, namely, (1) are the results of the different studies similar and to the extent that they are similar, (2) what is the best overall estimate, (3) how precise and robust is the estimate, and (4) can dissimilarities be explained. Exploratory analysis, such as regarding subgroups of patients who are likely to respond particularly well to a treatment, may generate promising new research questions. Meta-analysis identifies areas where further studies are needed. Meta-analysis provides robust evidence and may utilize a less biased sample of evidence. Physicians can now make decisions regarding the use of therapies or diagnostic procedures on the basis of a single article that synthesizes the findings of tens or hundreds of clinical studies. The Cochrane Collaboration which is an international organization involved in preparing meta-analysis of the effects of interventions in all aspects of health care. The science of meta-analysis is relevant to clinical and community psychiatry to evaluate the potential errors and sources of bias and offer guidelines for evaluation. The statistical basis of meta-analysis reached back to the 17th century wherein astronomy and geodesy intuition and experience suggested that combinations of data might be better than attempts to choose amongst them. Meta-analysis has had critics and criticisms over the years. Most prominent of which is publication bias, which refers to the tendency for journals and authors not to publish articles on research that has no significant findings. There is a danger that meta-analysis of observational data produce very precise but spurious results. The complex methods used in meta-analysis should always be complemented by clinical acumen and common sense in designing the protocol of a systematic review, deciding what data can be combined, and determining whether data should be combined. 3Meta-analysis provides an opportunity for shared subjectivity in reviews rather than true objectivity. Meta-analyses are most easily performed with the assistance of computer databases and statistical software.
