Systematic Literature Review (SLR)

A systematic literature review answers a focused question using an explicit, pre-specified and reproducible method. Unlike a narrative review, every decision — databases searched, search strings, inclusion and exclusion criteria, screening process, quality appraisal — is documented so another researcher could repeat it and reach the same set of studies.

The standard sequence is: formulate the question (often with a framework such as PICO or SPIDER), register or write a protocol, search multiple databases systematically, screen titles and abstracts against criteria, assess full texts, appraise methodological quality, extract data into a structured form, and synthesise.

Reporting follows the PRISMA guideline, whose flow diagram accounts for every record from identification through screening to final inclusion, including reasons for each exclusion at full-text stage. Screening independently by two reviewers with an agreement statistic strengthens credibility. Where the included studies report comparable effect sizes, the synthesis can extend into a meta-analysis.