Twelve years' experience with the Patient Generated Index (PGI) of quality of life: a graded structured review

The Patient Generated Index (PGI) is an individualised quality of life (QoL) measure that has been in use since 1994. Various adaptations have been made to suit a variety of client groups. The PGI's psychometric properties have been studied but their review is necessary to inform instrument choice. This article provides a structured review, using grading criteria adapted from those developed to aid outcome measure selection for use with older people. These criteria grade quality of evidence and strength of findings for psychometric validity, providing a useful model for future reviews. All published articles providing data addressing validity, reliability and/or responsiveness were included in the review. Eighteen relevant articles were identified and analysed using the grading criteria. Variable results and quality of investigation were seen. Generally the measure was found to be adequately reliable for group comparisons. The PGI appeared valid but evidence for responsiveness was unclear. Those versions of the measure using fewer points in their Likert scales may have higher reliability. Cognitions involved in QoL judgements remain little understood and investigations of psychometric properties may be enhanced by examination of appraisal processes.