What an integrative review is
An integrative review is a form of research synthesis that includes studies with different designs in one review. A review of how nurses recognize deterioration in ward patients, for example, may need randomized trials of early warning scores, cohort studies of missed signs, interview studies of how nurses decide and policy papers. A review limited to one design would leave out part of the answer.
Whittemore and Knafl described the method in 2005 as the broadest type of research review, one that allows the inclusion of experimental and non-experimental research to understand a phenomenon fully. It can also include theoretical literature. The aims vary. An integrative review can define concepts, review theories, appraise evidence on a clinical problem or analyze methodological issues in a field. Torraco, writing for human resource development, described a similar form that generates new frameworks and perspectives from existing literature.
The strength of the method is breadth, and its risk is the same: when anything can be included, a review without clear rules can become an unstructured selection of papers. The standard of rigor has risen, and many journals now expect integrative reviews to follow explicit search, selection and appraisal methods.
How it differs from other reviews
A systematic review usually addresses a narrow question and focuses on one type of evidence, most often trials, with a strict protocol and, where suitable, meta-analysis. A narrative review gives an expert overview without a prescribed method. An integrative review sits between them. It uses systematic steps for the search and selection, but accepts diverse designs and synthesizes by narrative and thematic methods rather than by pooling.
It is also related to the mixed-methods review. A mixed-methods review is typically built around a defined integration of quantitative and qualitative evidence with a planned design, while the integrative review is broader and may include non-empirical literature. The two overlap, and a review should say which it is and why.
A meta-analysis is not usual in an integrative review because the included studies measure different things in different ways. If a subset of studies is comparable, a meta-analysis of that subset can be added, provided it is reported as such.
The five stages
Whittemore and Knafl's framework has five stages. It remains the most cited guide, and reviewers who follow it have a clear structure for the protocol and the report.
| Stage | Task |
|---|---|
| 1. Problem identification | State the purpose and the question; define variables and the population of interest |
| 2. Literature search | Search several sources with a documented strategy; report databases, terms and limits |
| 3. Data evaluation | Appraise the quality of each primary source with a tool suited to its design |
| 4. Data analysis | Reduce, display, compare and draw conclusions; look for patterns, themes and gaps |
| 5. Presentation | Report the synthesis with enough detail for readers to judge and reproduce it |
Each stage should be recorded. The problem statement should be specific enough to guide inclusion decisions. A vague question such as "what is known about patient safety" leads to an unmanageable and unfocused review. A structured question that specifies the population, the phenomenon and the context, with outcomes where relevant, is more practical.
Searching and selecting
A broad review needs a broad search, and it needs to be documented. Use several databases that cover the disciplines involved (for nursing topics, CINAHL and MEDLINE are common, with PsycINFO, Embase or a database of education or social science research as needed), supplement them with reference-list checking and citation searches, and consider grey literature when policy documents are in scope. The strategy should be reported in full so that another team could repeat it.
Selection should use written criteria and, ideally, two reviewers for at least a sample of records. The number of records at each stage should be recorded. A PRISMA flow diagram works for integrative reviews even where the full checklist does not fit all items, and using it makes the process visible.
Because the review includes several designs, the inclusion criteria should say which designs are in and which are out, and why. Excluding all but English-language studies, for example, is a common choice that limits the findings and should be reported as a limitation.
Appraising studies of different designs
Quality appraisal is the hardest part of an integrative review, because no single tool fits randomized trials, cohort studies, interviews and case studies. Options include design-specific tools applied to each study type, or a single tool built for mixed designs, such as the Mixed Methods Appraisal Tool, which has criteria for qualitative, quantitative randomized, quantitative non-randomized, quantitative descriptive and mixed-methods studies.
Whichever approach is used, the review should state it, apply it consistently and use the results. Some reviews exclude studies below a threshold; others include all and report quality alongside the findings; others weight the synthesis. Each choice has consequences and should be justified. A table listing each study with its design, sample, main findings and appraisal outcome allows the reader to check the reasoning.
Scores should not be summed without thought. Different items matter differently, and a total score can hide a fatal flaw. Reporting the results of each appraisal domain is more informative.
Analysis and synthesis
Analysis in an integrative review moves from the individual studies to a unified account. Whittemore and Knafl describe data reduction (classifying the studies and extracting key points into a matrix), data display (tables, matrices and figures that make patterns visible), data comparison (looking for patterns, themes, contrasts and gaps) and conclusion drawing and verification.
In practice, many integrative reviews group studies by theme or by research question and discuss the weight of evidence in each group. Quantitative and qualitative results can be set side by side, with a statement about where they agree, disagree or address different aspects of the topic. The value lies in explaining the phenomenon, so the synthesis should go beyond a list of study summaries to say what the body of research shows, how certain it is and what is missing.
The conclusions should stay within the evidence. Because designs are mixed and appraisal may be uneven, an integrative review should avoid strong causal statements unless the trial evidence supports them, and it should say how far the findings apply to other settings.
A worked outline of an integrative review
Consider a review of how family members take part in decisions about care for older adults in hospital. The question is structured as population (hospitalized adults aged 65 and over and their family members), phenomenon (family participation in care decisions) and context (acute care settings). The aim is to describe the forms participation takes, the factors that help or hinder it and the outcomes reported.
The search covers MEDLINE, CINAHL and PsycINFO, with checks of reference lists. The inclusion rules accept trials of communication interventions, surveys, cohort studies and interview studies, but exclude opinion pieces. After screening, studies are classified into three groups: intervention studies, descriptive quantitative studies and qualitative studies. Each is appraised with the MMAT, and the results are shown by domain in a table.
The data display places the studies in a matrix with columns for design, setting, who took part, how participation was defined, the main findings and the quality rating. Comparing across the matrix shows that definitions of participation vary widely, that qualitative studies describe barriers that surveys do not measure, and that the few trials use outcomes that do not match what families say matters. These are the findings of an integrative review: a map of concepts, an account of how evidence of different kinds fits together and a list of gaps. The example is an illustration of the method and does not report findings from a real review.
Reporting and quality markers
No single reporting guideline is designed for the integrative review. The PRISMA 2020 statement is the nearest widely used standard and covers the search, selection and presentation of results; items that do not fit, such as meta-analysis, can be marked as not applicable. Registering the protocol in a public repository, where the platform allows, increases transparency, although some registries limit the review types they accept.
Markers of a sound integrative review include a focused question, a documented and reproducible search, explicit selection criteria and a flow diagram, appraisal of all included studies with a stated method, a table of characteristics, a synthesis that goes beyond summary, an honest limitations section and a clear statement of implications and research gaps. Readers and editors can use this list to judge the review.
Limitations
An integrative review is only as rigorous as its rules. Broad inclusion can lead to loosely defined questions and selective use of studies. Appraisal of mixed designs is uneven, and tools differ in what they measure. Synthesis is interpretive and can vary between reviewers. Because studies are not pooled, the review gives no single effect estimate and cannot, by itself, show how large an effect is. No reporting guideline fits it exactly. Findings should be presented as an account of the literature with its limits stated.
Evidence synthesis informs decisions about groups and policy. It does not replace professional judgment about an individual.
How we can help
Support for a integrative review
The work can be supported at different depths. Choose what you need, and the scope is agreed in writing before work begins.
Protocol and registration
A protocol and analysis plan written before the search, with registration prepared where appropriate.
Search and screening
Documented search strategies, screening and the flow diagram.
Appraisal and synthesis
Data extraction, risk of bias, certainty of evidence and the synthesis.
Manuscript and submission
Optional: the full paper, the reporting checklist and the submission materials.
Frequently asked questions
What is an integrative review?
A review that synthesizes studies of different designs, often quantitative and qualitative, to give a broad account of a topic.
How is it different from a systematic review?
A systematic review usually has a narrow question and one evidence type and may pool results. An integrative review accepts mixed designs and synthesizes by themes and comparison.
Can an integrative review include a meta-analysis?
It can for a subset of comparable studies, but usually it does not, because the outcomes and designs differ.
How do I appraise studies of different designs?
Use design-specific tools, or a tool built for mixed designs such as the MMAT, state the approach and report the results of each domain.
Which reporting guideline should I follow?
No guideline is specific to integrative reviews. PRISMA 2020 is the nearest standard, with items adapted as needed.
How many studies should an integrative review include?
There is no fixed number. The set should follow from the question and the written criteria, and the review should say how many records were found and why others were excluded.
References
- Whittemore R, Knafl K. The integrative review: updated methodology. J Adv Nurs. 2005;52(5):546-553.
- Torraco RJ. Writing integrative literature reviews: guidelines and examples. Hum Resour Dev Rev. 2005;4(3):356-367.
- Russell CL. An overview of the integrative research review. Prog Transplant. 2005;15(1):8-13.
- Hong QN, Fabregues S, Bartlett G, et al. The Mixed Methods Appraisal Tool (MMAT) version 2018 for information professionals and researchers. Educ Inf. 2018;34(4):285-291.
- Snyder H. Literature review as a research methodology: an overview and guidelines. J Bus Res. 2019;104:333-339.
- Page MJ, McKenzie JE, Bossuyt PM, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021;372:n71.