Table 1.

Differences between systematic and narrative reviews

Feature	Narrative review	Systematic review
Research question	Often unclear or broad	Specified and specific
Literature sources and search	Not usually specified	Comprehensive sources (more than one database) and explicit search strategy
Study selection	Not usually specified	Explicit selection criteria and selection by two independent reviewers
Quality assessment included studies	Not usually present or only implicit	Critical appraisal on the basis of explicit quality criteria
Synthesis	Often a qualitative summary	Often also a quantitative summary (meta-analysis)