Background: While Quality Of Life (QOL) in subjects suffering from schizophrenia has been studied using a variety of generic or specific instruments, only very few studies have analyzed the agreement between patients and proxy ratings on patients' QOL.
Methods: We administered the World Health Organization Quality of Life assessment instrument (WHOQOL-100) to 292 patients and the Quality of Life for Proxies (QOL-P) to their proxies, respectively; the QOL-P is a 30-item instrument derived from the WHOQOL-100 and adapted for administration to a key informant.
Results: Agreement between patients and proxies on the four main QOL areas was highest for the physical area (intraclass correlation coefficient, ICC = 0.41) and lowest for the psychological area (ICC = 0.29). In line with the results of other studies comparing patients' and proxies' ratings, proxies generally underestimated patients' physical and psychological QOL. Moreover, the agreement between patients' and proxies' ratings was consistently higher across all QOL areas when the proxy was a relative compared to a non-relative proxy.
Conclusions: The agreement between patients and proxies in QOL assessment is modest, but it is relatively higher when observable aspects of QOL are rated and when the proxy who makes the evaluation is a family member who has closer contacts with the patient. In order to obtain a comprehensive picture of patients' QOL, it would be advisable to compare patients' ratings with the assessments made by close informants.