A new approach to the measurement of quality of life. The Patient-Generated Index.

Quality of life has been defined as "the extent to which our hopes and ambitions are matched by experience." To improve a patient's quality of life through medical care would be to "narrow the gap between a patient's hopes and expectations and what actually happens." Using the above definition as a conceptual basis, we produced a self-administered, Patient-Generated Index (PGI) of quality of life. The PGI was completed by 359 patients presenting with low back pain. The validity of the measure was assessed by correlating patients' PGI scores with a well-validated health profile, the Short-Form 36-item Health Survey (SF-36), and with their scores on a clinical back pain questionnaire. Stepwise multiple regression was then used to model the relationship between the PGI score and the SF-36. Patients' PGI scores showed a high correlation with SF-36 scales measuring pain, social functioning, and role limitations attributable to physical problems, and with the clinical questionnaire. Together with whether a person was retired or not, these health variables were able to explain 25% of the variance in PGI scores. Patient generated index scores were significantly lower in patients referred to hospital compared with those managed solely in general practice and tended to reflect the general practitioner's assessment of symptom severity. We conclude that it is possible to construct a questionnaire that quantifies the effect of a medical condition on patients' quality of life in a way that has meaning and relevance in the context of their daily lives. The PGI has considerable potential for routine use in a wide range of clinical conditions for which the measurement of outcome has hitherto proved very difficult.