Integrative Review — Integrative Literature Review

A conventional systematic review typically restricts inclusion to a single study design — most often randomised controlled trials — and aims for a pooled quantitative estimate through meta-analysis. An integrative review broadens the inclusion criteria to encompass experimental, non-experimental, qualitative, and theoretical sources, making it more comprehensive but less suited to precise effect-size estimation. Both methods require explicit search documentation, inclusion criteria, and quality appraisal; the integrative review simply applies these rigours across a wider methodological landscape.

Both map a broad literature, but they differ in purpose and depth. A scoping review charts the extent and nature of evidence without performing formal quality appraisal or synthesising conclusions; it answers 'what research has been done?' An integrative review conducts quality appraisal of included studies and synthesises findings into substantive conclusions; it answers 'what does the evidence tell us?' Choose a scoping review when you need a landscape overview; choose an integrative review when you need evidence-based conclusions.

Standard PRISMA guidelines were designed for systematic reviews and meta-analyses, so not every PRISMA item maps perfectly onto an integrative review. However, the underlying principles — transparent search documentation, a flow diagram of study selection, and explicit reporting of methods — are equally applicable and widely expected by journal reviewers. Authors should follow PRISMA as closely as possible and note any deviations where the integrative design makes specific items inapplicable.

Yes, and for many research questions it is advisable. Grey literature — government reports, conference papers, dissertations, practice guidelines — often contains evidence not published in peer-reviewed journals, and excluding it can bias the synthesis toward positive findings. Searching grey literature sources such as ProQuest Dissertations, OpenGrey, and relevant professional organisation websites should be documented with the same rigour as database searches.

There is no minimum threshold. The appropriate sample size depends on the breadth of the research question and the density of the existing literature. A narrow question in a new field might yield 10–15 studies sufficient for meaningful synthesis; a broad question in an established field might require screening hundreds of records to arrive at 40–80 included studies. The aim is comprehensiveness relative to the search strategy, not a pre-determined number.