EQ-5D in patients with dementia - An investigation of inter-rater agreement

BACKGROUND. There are difficulties in obtaining health-related qualify of l ife (HRQL) data from patients with dementia due to variation in their cogni tive ability, degree of insight and capacity to make judgments. The use of proxies is one solution. OBJECTIVES. To examine the infer-rater agreement of patient and proxy compl etion of the EuroQol EQ-5D instrument (EQ-5D). RESEARCH DESIGN. The EQ-5D instrument was completed separately by patients, their caregivers and a physician. Assessment of inter-rater agreement invo lved comparison of self-completed (patient) and proxy completed (caregiver and physician) responses for each dimension of EQ-5D; using a weighted kapp a score. Three key hypotheses were tested. (1) Interrater agreement would b e stronger between patient and caregiver than between patient and physician . (2) Interrater agreement would be stronger on the `observable' and object ive dimensions of EQ-5D. (3) Interrater agreement between patient and proxi es would be stronger for patients with earlier dementia. SUBJECTS. The sample comprised 64 patients with a range of dementia severit y. MEASURES. The EQ-5D health state classification system and visual analogue scale were used to assess HRQL. Global severity of dementia was determined using the Clinical Dementia Rating Scale. Results. The principal finding of this study was that responses to EQ-5D qu estions were highly variable across the three raters such that none of the three hypotheses were strongly supported. Conclusions. The data provide some support for the use of EQ-5D when interv iewer administered. However, there are serious concerns regarding the valid ity of patient self-rated HRQL data obtained in this study and uncertainty exists regarding who the appropriate proxy should be, as different groups o f proxies provide different results. It was not clear whether caregivers or physicians represent better proxies. Further research should focus on the comparison of caregivers and physicians as proxies.