A practical Guide to do Primary research on Meta
analysis Methodology

2. Systematic Review and Meta-Analysis

Systematic reviews include a comprehensive search strategy that allows the reviewers to recognize all related studies in a particular topic. Systematic reviews have the potential to produce information-rich databases which permit extensive secondary analysis. Examine the pool of existing information. Search standards must be sensitive enough not to miss relevant studies. Important terms and concepts conveyed as index terms and synonymous keywords, such as Medical Subject Headings, must be collected using Boolean operators AND, OR and NOT. Wildcards, Truncation and proximity operatives can help improve the search strategy by providing different wording for the same concept and spelling variation. Searching approaches can be validated using a selection of expected relevant studies. If some strategy fails to retrieve one among the selected studies, the research strategy needs further optimization. Updating the search strategy in every iterative step continues until the search strategy performs at a satisfactory level. A comprehensive prediction to return a vast number of studies is not relevant to the topic, usually resulting in a specificity of <10%.  Hence, the starting stage, i.e. examining through the library to choose related studies, is time-consuming and is open to human error. Nevertheless, systematic reviews can provide the highest-quality quantitative evidence synthesis to directly inform the experimental and computational basic, preclinical and translational studies.

3. Rapid Review and Meta-Analysis

The objective of the rapid review, as mentioned in the name, it helps in reducing the time needed to synthesize the data. Rapid reviews are an appropriate alternative to systematic approaches if reviewers prefer to get a general idea of the field’s state without a prolonged time investment. Search policies are constructed by increasing search specificity, decreasing the number of inappropriate studies discovered by searching comprehensiveness cost. A rapid review’s strength is its flexibility to adapt to the reviewer’s needs, resulting in a lack of standardized methodology.

Common shortcuts made in rapid reviews are:

• Narrow down the search criteria,

• Striking date restrictions,

• Conducting the review with a single reviewer,

• Neglecting expert consultation (i.e., librarian for search strategy development),

• Constricting language criteria (ex. English only),

• Preceding the iterative process of searching and search period selection,

• Neglecting quality checklist criteria and

• Limiting the number of databases searched.

These shortcuts will restrict the initial pool of studies returned from the search, thus advancing the selection process, potentially result in the segregation of relevant studies and the introduction of selection bias.  Rapid reviews do not reflect detriment quality or synthesize misrepresentative results.

While there is consent that rapid reviews do not sacrifice quality or synthesize misrepresentative results, it is suggested that critical outcomes be later confirmed by systematic review. Nevertheless, rapid reviews are a feasible alternative when parameters for computational modelling need to be valued. While systematic and rapid reviews rely on various strategies to select the related studies, the statistical methods used to produce data from the systematic and rapid review are identical.

4. Screening and Selection

When the literature search is wide-ranging, articles are taken out and stored in a place manager for screening. Before research screening, the addition and elimination criteria must be defined to ensure constancy in study identification and recovery, especially when multiple reviewers are involved. The serious steps in screening and selection are

• Eliminating duplicates

• Screening for related studies by title and abstract, and

• Inspecting full texts to make sure they fulfil the suitability criteria.

Some reference managers accessible, including Mendeley and Rayyan, exactly developed to help with screening systematic reviews.

However, 98% of journalists report using Endnote, Reference Manager or RefWorks to prepare their reviews. Reference managers often have duplication functions; however, these can be tedious and error-prone. A protocol for faster and more reliable duplication in Endnote has been recently proposed. The articles’ selection should be suitably broad, not subject to a single lab or author. In primary research articles, it is collective to find data sets reused by the same group in multiple studies. Therefore, additional securities should be taken when determining to contain multiple studies published by a single group. Screening and selection procedure, the reviewer acquires a complete list of good full-text manuscripts. The full screening and selection procedure should be stated in a PRISMA diagram, which maps the data flow throughout the review according to arranged guidelines published elsewhere.