Purpose: This study aimed to assess the agreement between patient and proxy ratings of Quality of life (QoL) in patients with psychotic mental illnesses.
Methods: The abbreviated version of the WHO quality of life scale (WHOQOL-BREF) and 36-item short-form health survey (SF-36) were administered to patient-family proxy pairs of 81 schizophrenia patients with mild symptoms and 50 euthymic bipolar disorder patients. Paired t-tests and the intraclass correlation coefficient (ICC) were used to evaluate the level of agreement between patient and proxy ratings of QoL.
Results: At the group level, small standardized differences (0.0-0.3 for schizophrenia, 0.0-0.5 for bipolar disorder) between patient and proxy mean scores were found for most domains in both QoL measures. At the individual level, moderate to good agreement (ICC) was found (schizophrenia: ICC 0.4-0.7 on WHOQOL-BREF; 0.4-0.7 on SF-36; bipolar disorder: ICC 0.4-0.7 on WHOQOL-BREF; 0.6-0.7 on SF-36). The reported agreement was higher than that reported for similar measures in the psychiatric population. These results may be due to the fact that our subjects had mild clinical symptoms and frequent family interaction.
Conclusion: These findings suggest that family proxy rating of patients' QoL can be used as a reasonable estimate of the patients' QoL for stable schizophrenia and bipolar patients in Korea.