Validation of an individualised quality of life measure in older day hospital patients

BACKGROUND: To test the ease of use, reliability, responsiveness and construct validity of the Patient Generated Index, an individualised quality of life score, in older people attending a Medicine for Older People Day Hospital. METHODS: Prospective longitudinal study in patients attending a specialist Medicine for Older People Day Hospital in Scotland. The Patient Generated Index was administered at baseline, one week later, and at the end of Day Hospital attendance. Functional Limitations Profile, Hospital Anxiety and Depression Score, Barthel index and global subjective impressions of change were also collected and compared with baseline scores and change in Patient Generated Index scores. Reliability was assessed using intraclass correlation coefficients in subjects reporting no change in global quality of life; responsiveness was assessed using effect size and Guyatt coefficients in subjects reporting change in global quality of life. External validity was assessed via correlation with measures of physical function, comorbid disease and psychological state. RESULTS: 75 patients were enrolled, mean age 81 years. Mean completion time was 5.0 minutes at baseline. Reliability was moderate (intraclass correlation coefficient 0.72) but there were weak and inconsistent responses to change (effect sizes 0.02 to 0.15; Guyatt responsiveness coefficient 0.29). Patient Generated Index scores correlated with Functional Limitation Profile scores (r = 0.51, p < 0.001), baseline anxiety score (r = -0.25, P = 0.039) and baseline depression score (r = -0.37, P = 0.002) but displayed only weak, non-significant correlation with number of comorbid diseases (r = -0.22, P = 0.07), number of medications (r = -0.21, P = 0.08) and Barthel score (r = 0.09, p = 0.45). CONCLUSION: The Patient Generated Index appears moderately reliable and easy to complete, but is poorly responsive to change, limiting its usefulness in clinical practice or research.