Extension of a systematic review that employs statistical techniques to pool the data from the literature in order to calculate a cumulative effect size. This is done to answer a clearly defined a priori question.
Although all medicine based on science has some degree of empirical support, evidence based medicine (EBM) goes further, classifying evidence by its epistemologic strength and requiring that only the strongest types (coming from metaanalysis, systematic reviews, and randomized controlled trials) can yield strong recommendations; weaker types (such as from case control study) can yield only weak recommendations.
see MOOSE Guidelines
Despite their increasing popularity in the neurosurgery literature, meta-analyses have not been scrutinized in terms of reporting and methodology.
Klimo et al. sought to answer 4 specific questions: Are metaanalysis improving
1) with time;
2) when the study met their definition of a meta-analysis;
3) when clinicians collaborated with a potential expert in meta-analysis
4) when the meta-analysis was the only focus of the paper?
Results Seventy-two meta-analyses were published in the JNS Publishing Group journals and Neurosurgery between 1990 and 2012. The number of published meta-analyses has increased dramatically in the last several years. The most common topics were vascular, and most were based on observational studies. Only 11 papers were prepared using an established checklist. The average AMSTAR and PRISMA scores (proportion of items satisfactorily fulfilled divided by the total number of eligible items in the respective instrument) were 31% and 55%, respectively. Major deficiencies were identified, including the lack of a comprehensive search strategy, study selection and data extraction, assessment of heterogeneity, publication bias, and study quality. Almost one-third of the papers did not meet our basic definition of a meta-analysis. The quality of reporting and methodology was better 1) when the study met our definition of a meta-analysis; 2) when one or more of the authors had experience or expertise in conducting a meta-analysis; 3) when the meta-analysis was not conducted alongside an evaluation of the authors' own data; and 4) in more recent studies.
Reporting and methodology of meta-analyses in the neurosurgery literature is excessively variable and overall poor. As these papers are being published with increasing frequency, neurosurgical journals need to adopt a clear definition of a meta-analysis and insist that they be created using checklists for both reporting and methodology. Standardization will ensure high-quality publications 1).