Development and psychometric properties of a disease-specific quality of life questionnaire for adult patients with growth hormone deficiency

Abstract

BACKGROUND: Adults with growth hormone (GH) deficiency (GHD) may experience physical and psychological disturbances, which can affect their quality of life (QOL). OBJECTIVES: To develop and validate a disease-specific module from the previously published QOL measure Questions on Life Satisfaction Modules (QLS(M)): the QLS(M)-H that specifically addressed the needs of patients with hypopituitarism. A second aim was for the questionnaire to be applicable across different cultural backgrounds in order to evaluate the efficacy of therapy in large, international clinical trials, thus providing additional clinical endpoints for these studies. DESIGN: A preliminary German language version of the QLS(M)-H was developed from 26 semi-structured interviews of adults with GHD. The questionnaire was then independently translated into five other languages and applied in open, non-controlled, multicentre, longitudinal studies to patient (n=717) and normative populations (n=2700). METHODS: A revised, nine-item version of the questionnaire was developed, based on previously defined criteria, and was evaluated for reliability and validity. Sensitivity to detect changes after GH replacement was also assessed. RESULTS: The 16 items of the preliminary questionnaire were reduced to nine items on the basis of the correlation of items/factors from initial patient interviews. Psychometric analysis revealed the reliability of the nine-item scale. The Cronbach's alpha scores ranged from 0.81 to 0.89 and the test-retest correlations ranged from 0.76 to 0.88, all of which indicate reliability over time. Mean scores increased significantly during GH replacement therapy, with observed changes greater than those seen with the non-specific modules of the QLS(M), indicating the sensitivity of the scale. CONCLUSIONS: The QLS(M)-H questionnaire is concise, easy to complete, and can be effectively applied across different cultural backgrounds. Psychometric evaluation of the questionnaire reveals that it is a valid, reliable and sensitive tool useful for assessing impaired life satisfaction in adult patients with GHD and also for monitoring the efficacy of GH therapy.