Validity of health-related quality of life subscales.

This report assesses the validity of subscales from the Quality of Life Index (QLI). Subscale validity is tested across different samples of patients with cancer and other diseases. The results of the factor analyses of different versions of the QLI tested in six studies confirm four important health-related quality of life dimensions. These dimensions are psychological well-being, physical well-being, symptoms/side effects, and nutrition. Psychological well-being is represented by a satisfying life, having a good (general) quality of life, having fun, feeling happy and enjoying life. Physical well-being is defined by tiring easily (fatigue), ability to work/carry out usual tasks, strength, and feeling healthy. The symptoms/side effects dimension is characterized by nausea, vomiting, pain distress, and perhaps, by pain amount and pain frequency. Finally, the nutrition dimension is represented by able to eat/eat sufficiently, eating pleasure/appetite, worry about weight, and possibly also taste changes. Good construct validity can be attributed to these health-related quality of life subscales.