Scoping reviews aim to identify and map the breadth of available evidence in a field of study. A scoping review may be undertaken when there is little data available on a topic and can be done as a precursor to a systematic review, and to determine if a full systematic review is feasible or relevant to undertake. A scoping review aims to:

• identify the extent and nature of available evidence in a given field
• clarify key concepts/ definitions in the literature
• examine how research is conducted on a certain topic or field
• identify key characteristics or factors related to a concept
• identify and analyse knowledge and research gaps in the existing literature

Although a scoping review output is different to a systematic review, it still requires the same rigorous and transparent methods to ensure that the results are trustworthy.

Munn, Z., Peters, M.D.J., Stern, C., Tufanaru, C., McArthur, A. and Aromataris, E., 2018. 'Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach'. BMC Med Res Methodology, vol. 18, no.143. https://doi.org/10.1186/s12874-018-0611-x

Rapid reviews aim to answer clinically urgent or time sensitive questions and follow the same steps and explicit and rigorous methodology as systematic reviews, but are generally completed in a shorter time frame. As such, researchers take legitimate shortcuts in order to deliver findings more rapidly than in a standard systematic review. Possible shortcuts may include:

• searching: sources are limited but must still be transparent and reproducible
• narrow time frame: usually under 5 weeks
• no hand searching due to time constraints
• can be done by a single person selecting and screening
• appraisal: still critical and rigorous

Douba, Z., 2022, July 20. 'What are ‘rapid reviews’ and why do we need them?' Students 4 Best Evidence [Blog]. https://s4be.cochrane.org/blog/2022/07/20/what-are-rapid-reviews-and-why-do-we-need-them/

A meta-analysis is the quantitative analysis of the results included in a systematic review. This is a statistical method that combines the results of several trials to generate an average result. Meta-analysis adds value because it can produce a more precise estimate of the effect of a treatment than considering each study individually.

While meta-analysis can improve the precision of an effect estimate, it can also be misleading if it is performed with data that are not sufficiently similar, or with data whose methodological quality is poor (for example, because the study participants were not properly randomised). So it’s not always appropriate to use meta-analysis and many systematic reviews do not include them. Reviews that do not contain meta-analysis can still synthesise study data to produce something that has greater value than the sum of its parts.

Mellor, L., no date. 'The difference between a systematic review and a meta-analysis', Covidence [Blog]. https://www.covidence.org/blog/the-difference-between-a-systematic-review-and-a-meta-analysis/

An integrative review is a broad type of literature review that combines research studies conducted using various methodologies to encapsulate diverse perspectives to better understand the current state of evidence related to a particular phenomenon or healthcare problem.

An integrative review is best designed to:

• review experimental and non-experimental research simultaneously
• define concepts
• review theories
• review evidence/point out gaps in the literature
• analyse methodological issues

Gunberg Ross, J., Latz, E., Meakim, C.H., Arcamone, A., Furman, G. and Reynolds, K., 2022. 'Multiple-Patient Simulations and Student Outcomes in Prelicensure Nursing Education: An Integrative Review', Clinical Simulation in Nursing, vol. 64, pp.31-45. https://doi.org/10.1016/j.ecns.2021.11.007

Whittemore, R. and Knafl, K., 2005. 'The integrative review: updated methodology'. Journal of Advanced Nursing, vol. 52, no. 5, pp.546–553. https://doi.org/10.1111/j.1365-2648.2005.03621.x

Mixed methods reviews combine qualitative and quantitative evidence synthesis approaches. They integrate findings from both qualitative and quantitative studies to provide a more comprehensive understanding of the research question. Mixed methods reviews are particularly useful when the research question requires insights from both types of evidence.

Mixed methods reviews are best designed for:

• multidisciplinary topics or topics with a body of literature that includes quantitative, qualitative, and mixed methods studies
• determining not only the effects of interventions but also their appropriateness
• identifying research gaps
• providing an explanation for possible heterogeneity between trials
• answering multiple questions in one systematic review

Ahmad, B., no date. 'Streamlining Research: Unveiling the Power of Evidence Synthesis with Covidence', Covidence [Blog]. https://www.covidence.org/blog/the-difference-between-a-systematic-review-and-a-meta-analysis

Harden, A., 2010. 'Mixed-Methods Systematic Reviews: Integrating Quantitative and Qualitative Findings', NCDDR: FOCUS - Technical Brief, no.25. https://ktdrr.org/ktlibrary/articles_pubs/ncddrwork/focus/focus25/Focus25.pdf 

An umbrella review is essentially an overview of existing systematic reviews. If current, multiple, good quality, systematic reviews exist about a given topic or question, rather than conduct another review addressing the same issue, a reviewer may use these available systematic reviews to summarise and synthesise the findings. Umbrella reviews offer the possibility to address a broad scope of issues related to the topic of interest. They focus on a broad condition or problem for which there are competing interventions and highlight reviews that address these interventions and their results.

Umbrella reviews may:

• include analyses of different interventions for the same problem or condition
• analyse the same intervention and condition, but different outcomes
• analyse the same intervention but different conditions, problems or populations

Aromataris, E., Fernandez, R., Godfrey, C., Holly, C., Khalil, H. and Tungpunkom, P., 2020. 'Chapter 10: Umbrella Reviews', in Aromataris, E. and Munn, Z. (eds). JBI Manual for Evidence Synthesis. https://doi.org/10.46658/JBIMES-20-11