Objective: To develop and validate a short, global, and generic quality of life (QoL) questionnaire for clinical databases. The construct validity and item weighting of existing questionnaires are increasingly questioned.
Design: Cross-sectional population study.
Subject: 2460 Danes aged 18-88 years, randomly selected through the Danish Central Person Registry.
Interventions: Ten questions covering the spectrum of the integrative theory of QoL together with the Nottingham Health Profile (NHP), Sickness Impact Profile (SIP), and self-estimated QoL questionnaire were sent by mail. A test-retest study of 50 people was conducted after one month.
Main outcome measures: Construct and criterion validity, reliability, and sensitivity.
Results: QoL5 correlations with SIP, NHP, Self-estimated QoL were 0.37, 0.52, and 0.76, respectively, and increased among those who were unwell. Cronbach's alpha was 0.69. All correlations in Siegel's test were over 0.6, and the test-retest correlation was 0.82. Only 12 respondents in each group will be needed to detect a difference of 10% in the QoL score between two groups.
Conclusions: QoL5 is a valid global and generic QoL measurement. Despite the use of only five questions, internal consistency and sensitivity were acceptable. So a relevant and practical outcome measurement is available for clinical databases.