Characteristics and implications of attrition in health-related quality of life studies in palliative care.

In a longitudinal study of 297 palliative care patients, 280 patients were followed from inclusion to death. Characteristics and health-related quality of life (HRQL) of the participants and those who later dropped out were compared at inclusion, and 3 and 2 months before their death. At inclusion, the dropouts were older (P = 0.001), had reduced Karnofsky performance score (P < 0.001), received more help from the local authority (P = 0.004) and had reduced HRQL compared with patients who continued in the study and completed the next questionnaire. There were no differences in any of the HRQL parameters between participants and dropouts 3 months before death. Two months before death, differences in HRQL were found, but in favour of the dropouts. Data from patients close to death may be representative of a larger group of patients, whereas initial dropouts may lead to a positive bias of reported HRQL.