There are over 30 types of<unk>  and the Table 1 below summarises some of these, but it is not exhaustive. It is important to note that there is not always consensus on the boundaries and distinctions between the approaches described below. +Table 1: A summary of some of the types of<unk> .<unk>  type Summary Mapping<unk> /systematic map A mapping<unk>  maps existing literature and categorizes data. The method characterizes quantity and quality of literature, including by study design and other features. Mapping<unk> s can be used to identify the need for primary or secondary research. Meta-analysis A meta-analysis is a statistical analysis that combines the results of multiple quantitative studies. Using statistical methods, results are combined to provide evidence from multiple studies. The two types of data generally used for meta-analysis in health research are individual participant data and aggregate data (such as odds ratios or relative risks). Mixed studies<unk> /mixed methods<unk>  Refers to any combination of methods where one significant stage is a literature<unk>  (often<unk> . It can also refer to a combination of<unk>  approaches such as combining quantitative with qualitative research. Qualitative<unk> /qualitative evidence synthesis This method for integrates or compares findings from qualitative studies. The method can include 'coding' the data and looking for 'themes' or 'constructs' across studies. Multiple authors may improve the 'validity' of the data by potentially reducing individual bias. Rapid<unk>  An assessment of what is already known about a policy or practice issue, which uses<unk>  methods to search for and critically appraise existing research. Rapid<unk> s are still a<unk> , however parts of the process may be simplified or omitted in order to increase rapidity. Rapid<unk> s were used during the COVID-19 pandemic.<unk>  A<unk>  search for data, using a repeatable method. It includes appraising the data (for example the quality of the data) and a synthesis of research data.<unk>  search and<unk>  Combines methods from a 'critical<unk> ' with a comprehensive search process. This<unk>  type is usually used to address broad questions to produce the most appropriate evidence synthesis. This method may or may not include quality assessment of data sources.<unk> ed<unk>  Include elements of<unk>  process, but searching is often not as comprehensive as a<unk>  and may not include quality assessments of data sources. Scoping<unk> s Scoping<unk> s are distinct from<unk> s in several important ways. A scoping<unk>  is an attempt to search for concepts by mapping the language and data which surrounds those concepts and adjusting the search method iteratively to synthesize evidence and assess the scope of an area of inquiry. This can mean that the concept search and method (including data extraction, organisation and analysis) are refined throughout the process, sometimes requiring deviations from any protocol or original research plan. A scoping<unk>  may often be a preliminary stage before a<unk> , which 'scopes' out an area of inquiry and maps the language and key concepts to determine if a<unk>  is possible or appropriate, or to lay the groundwork for a full<unk> . The goal can be to assess how much data or evidence is available regarding a certain area of interest. This process is further complicated if it is mapping concepts across multiple languages or cultures. As a scoping<unk>  should be<unk> ally conducted and reported (with a transparent and repeatable method), some academic publishers categorize them as a kind of<unk> ', which may cause confusion. Scoping<unk> s are helpful when it is not possible to carry out a<unk>  synthesis of research findings, for example, when there are no published clinical trials in the area of inquiry. Scoping<unk> s are helpful when determining if it is possible or appropriate to carry out a<unk> , and are a useful method when an area of inquiry is very broad, for example, exploring how the public are involved in all stages<unk> s. There is still a lack of clarity when defining the exact method of a scoping<unk>  as it is both an iterative process and is still relatively new. There have been several attempts to improve the standardisation of the method, for example via a PRISMA guideline extension for scoping<unk> s (PRISMA-ScR). PROSPERO (the International Prospective Register of<unk> s) does not permit the submission of protocols of scoping<unk> s, although some journals will publish protocols for scoping<unk> s.
Systematic review
Natural history study
Subgroup analysis
Platform trial
Clinical study report
Electronic patient-reported outcome
Cohort study
Intersalt study