Development of a disease-specific quality of life questionnaire in Addison's disease.

Context: Patients with Addison's disease reproducibly self-report impairment in specific dimensions of general well-being questionnaires, suggesting particular deficiencies in health-related quality-of-life (HRQoL).
Objective: We sought to develop an Addison's disease-specific questionnaire (AddiQoL) that could better quantify altered well-being and treatment effects. Design, Setting, Patients, Intervention, and Outcomes: We reviewed the literature to identify HRQoL issues in Addison's disease and interviewed patients and their partners in-depth to explore various symptom domains. A list of items was generated, and nine expert clinicians and five expert patients assessed the list for impact and clarity. A preliminary questionnaire was presented to 100 Addison's outpatients; the number of items was reduced after analysis of the distribution of the responses. The final questionnaire responses were assessed by Cronbach's alpha and Rasch analysis.
Results and Interpretation: Published studies of HRQoL in Addison's disease indicated reduced vitality and general health perception and limitations in physical and emotional functioning. In-depth interviews of 14 patients and seven partners emphasized the impact of the disease on the emotional domain. Seventy HRQoL items were generated; after the expert consultation process and pretesting in 100 patients, the number of items was reduced to 36. Eighty-six patients completed the final questionnaire; the responses showed high internal consistency with Cronbach's alpha 0.95 and Person Separation Index 0.94 (Rasch analysis).
Conclusions: We envisage AddiQoL having utility in trials of hormone replacement and management of patients with Addison's disease, analogous to similar questionnaires in GH deficiency (AGHDA) and acromegaly (AcroQoL).