Good review practice: a researcher guide to systematic review methodology in the sciences of food and health

Do you need a scoping study?

A scoping study is usually carried out before a full systematic review, to assess the breath of the research around the topic of interest. It may be used to determine how well the subject is researched and whether there is enough evidence or a real need to conduct a full systematic review. They are also planned to map keywords to relevant concepts and put the research topics in context. Scoping exercises are not mandatory and are only planned if there is a need to overview the state of the art for the topic of interest. 

In relevance to systematic reviews, they are widely used to:

• investigate the volume and state of available literature, 
• map concepts, keywords, and policies,
• to narrow down the scope of broad questions and make them suitable for the use of the SR methodology. 

The method of scoping research topics was first developed by the EPPI-Centre to pilot systematic reviews of environmental questions. They were then extended to clinical and social science topics and are gradually being adopted in other scientific disciplines.

How to conduct a scoping study

Scoping studies are descriptive and often not comprehensive, but they provide a roadmap of literature. They follow similar steps to a systematic review process to summarise the state of current research on a topic without the need for data extraction, quality assessment or sensitivity analysis. 

A standard framework proposed by Arksey, and O’Malley  [2] is commonly used in clinical and healthcare research. This framework can be adapted and applied in other fields as well.  

It consists of the following 5 steps: 
   Step 1: Identifying the research question,
   Step 2: Identifying relevant studies, 
   Step 3: Study selection, 
   Step 4: Charting the data, 
   Step 5: Collating, summarising, and reporting results.

Identifying the research question: the objective of the review question and the purpose of the scoping study determine which aspects of the study are important and what details are needed to provide an appropriate description. For example, to assess different applications of an intervention, a map of relevant literature to find all subpopulation might be planned.

Identifying relevant studies: regardless of the topic, at least 2 key elements of the research question set the foundation for a scoping study: the population and the outcome of interest. But unlike systematic review questions scoping questions seek to describe important aspects of relevant research. For instance, an intervention question can be centered around “what kind” of interventions have been applied to a particular subject for an outcome of interest.

Study selection: the search strategies of scoping studies are often designed to capture a broader spectrum of literature. As a result, the study selection process often is done at two different levels to manage the volume. First, all irrelevant and out of focus literature are removed by screening through citations or titles and abstracts. Then the screening procedure is followed for the full texts of relevant literature. 

Charting the data: this stage of the scoping method can differ considerably based on the purpose. These details can include study characteristics, details of the populations, type and volume of relevant primary studies, details of various concepts and topics, etc. 

Collating, summarising, and reporting results: The presentation formats are also guided by the purpose of the scoping review and often consist of tabulated forms that are used to organise and chart the data accordingly. When inputs or agreements from different field experts are needed, an optional consultation step is sometimes carried out in the end.

Good practice point: For the purpose of good practice this stage should be managed by at least 2 reviewers to make sure all relevant literatures are included. If the scoping review is intended for publication, a protocol should be developed before undertaking it, to outline the methods and objectives. 

Links to access examples of scoping studies