It is important to consider who the stakeholders for your systematic review are, and to involve representatives of key groups of people. Key groups to consider include: patients and their family memberscarershealthcare professionalshealth policy makershealth fundersdecision makers working in the relevant field. For a systematic review being conducted as part of a guideline development, the stakeholders for the review may be identical to the stakeholders for the guidelines. However, there may also be some differences. For example, if a systematic review is focused on a specific intervention or a population of people with a particular impairment or activity limitation, then it may be important to consider involving people with relevant specific lived experience. The 7Ps framework (Concannon et al. 2012), shown in table 1, can be a useful framework for identifying who to involve. Although it has been developed for a US situation, and for involving people in identifying and prioritising outcomes for research on an intervention’s effectiveness, the principles can be applied in other parts of the world, and in other types of research. Table 1 The 7Ps Framework to help identify who to involve in health research (Concannon et al. 2012 edited) CategoryDescriptionPatients and the publicCurrent and potential consumers of patient-centred healthcare and population-focused public health, their caregivers, families, and patient and consumer advocacy organisationsProvidersIndividuals (for example, nurses, physicians, mental health counsellors, pharmacists, and other providers of care and support services) and organisations (for example, hospitals, clinics, community health centres, community-based organisations, pharmacies, emergency medical services agencies, skilled nursing facilities, schools) that provide care to patients and populationsPurchasersEmployers, the self-insured, government and other entities responsible for underwriting the costs of healthcarePayersInsurers, Medicare and Medicaid, state insurance exchanges, individuals with deductibles, and others responsible for reimbursement for interventions and episodes of carePolicy makersThe White House, Department of Health and Human Services, Congress, states, professional associations, intermediaries, and other policy-making entitiesProduct makersDrug and device manufacturersPrincipal investigatorsOther researchers and their funders In deciding who to involve it is important to consider the aim of the PPI and, therefore, the range of perspectives that are needed to meet that aim. For example, if the aim is to have general oversight of the review conduct, then perhaps, people with a general perspective need to be involved. But if the aim is to identify the outcomes of greatest importance to people with lived experience of a particular health condition, then it will be essential to involve people with relevant lived experience. Often, for PPI, what is of greatest importance is that the people involved have a lived experience of a particular health condition. Generally, knowledge or familiarity with research methods and technical terms is not a requirement for involvement. It is good practice to write a role specification that describes, in plain language, the experience or attributes that people you involve should have. Also consider the potential benefits for people who volunteer to get involved in a systematic review, and make these clear. For example, these could include payment, authorship, acknowledgement, training, or impacting on an area of research that is important to them. The National Institute for Health Research (NIHR) webpage on people in research has examples of descriptions of people sought to involve in health research. How to recruit people After identifying the key groups of people to involve, strategies are required to find relevant individuals to approach and invite to get involved. The chapter on how to recruit and support patients and the public, and overcome barriers to their involvement in guideline development highlights different ways of identifying and reaching out to patient and public groups. Two broad strategies commonly used to find people to be involved in systematic reviews are: An open recruitment strategy, in which opportunities for involvement are advertised to the general population, and anyone can volunteer to get involved (for example, advertising on the NIHR’s People in research webpage). Open strategies can be:Fixed: After a group has been formed, advertising ceases and no new members are added.Flexible: Advertising for new members is ongoing and group membership can fluctuate. This may mean that a series of workshops has different group members, or some group members may attend more than once.A closed, or targeted, strategy, in which individual people, or individual groups, are invited to be involved. There are several strategies for recruiting a targeted group:Invitation: People known by name (or reputation) to the researchers will be invited to get involved. This can also be described as ‘nomination’.Existing groups: Rather than recruiting specific named individuals, the membership of an existing group is invited to get involved. Because different groups vary in how they operate, this can impact on the membership. In some cases, a group may have closed membership (that is, the same individuals make up the group), and sometimes a group may have open membership (that is, the group membership changes over time).Purposive sampling: A qualitative research framework is used for recruitment, generally aimed at getting representation of people with key pre-determined characteristics, experience or expertise. Although this results in a ‘targeted’ group, with closed membership, the strategies for identifying the population from which to sample can be similar to those for open involvement (that is, advertising). How many people to involve How many people you involve in your systematic review will depend on several factors. A key factor is the aim of PPI and, linked to the aim, how you are going to involve people (see the section on how to involve people in a systematic review). The factors listed in the section on choosing who, when and how for your review will also influence decisions about how many people to involve. The numbers to involve will also depend on the different groups of people that you want to have represented (see the section on who to involve in a systematic review). Work in partnership with the people you involve to ensure that they are comfortable with the number and range of people involved. When small numbers of people are involved, for example, as members of a steering or advisory group, ask them if they feel they can represent the different viewpoints, or whether additional input is required. In an exploration of PPI in a range of systematic reviews, Pollock et al. (2018) found that for: face-to-face meetings, the number of people involved ranged from 2 to 27one-off events, often advertised as open to the general public, the number of people involved ranged from 15 to 81involvement that did not require a face-to-face meeting, for example using an electronic Delphi or survey, the numbers invited ranged from 29 to 340 people.