International development of the quality of life in depression scale (QLDS)

Background: The Quality of Lifts in Depression Scale (QLDS) employs the nee ds-based model of quality of life (QoL) and was developed in the UK and The Netherlands as an outcome measure for clinical trials. This paper describe s the production and psychometric assessment of nine new language versions for Canada (French and English), Denmark, France, Germany, Italy, Morocco, Spain and the US. Methods: Three adaptation stages were employed; productio n of conceptually equivalent translations, field-test interviews and assess ment of reliability and construct validity by survey of patients with major depression. Results: Few problems were experienced with producing conceptu ally equivalent translations, except in Morocco. Patients in the field-test interviews found the instrument to have appropriate content and to be easy to complete. Internal consistency and test-retest reliability were excelle nt for all language versions and scores were found to relate appropriately to measures of depression severity and health status. Limitations: Further investigation is required of the ability of the measure to assess individua ls at the extremes of the QoL continuum. Data collected with the Arabic QLD S should not be combined with those from other countries. Conclusions: The QLDS is the first instrument designed to assess QoL in depression based an a coherent model of the construct, Each language version has been shown to be well accepted by respondents and to have excellent psychometric properti es. As the instrument is now available in a large number of languages, the QLDS is the QoL instrument of choice for inclusion in clinical trials of in terventions for depression, (C) 2001 Elsevier Science B.V. All rights reser ved.