Fig. 4

Levels of best practice for PPI in SPCR projects, according to Boote et al’s quality indicators [25]. ^ Combination of two quality indicators linked with expenses: travel costs and indirect costs (e.g. carer costs); * Combines three quality indicators: ‘contribution of PPI included in research reports and papers’, ‘PPI acknowledged in research reports and papers’ and ‘details of PPI reported in research reports and publications’. Data obtained from a PubMed search for articles associated with the 15 projects included in the analysis; ^# Adaptation of the quality indicator: ‘PPI offered mentors for personal and technical support’; ^$ Adaptation of the quality indicator: ‘Research findings were distributed to patients involved in the research in an appropriate format’