Development of a Disease-Specific Quality of Life Questionnaire in Addison's Disease

Kristian Løvås*, Suzanne Curran, Marianne Øksnes, Eystein S. Husebye, Felicia A. Huppert,  and V. Krishna K. Chatterjee

Department of Medicine (K.L., S.C., V.K.K.C.), University of Cambridge, Cambridge CB2 0QQ, United Kingdom; Institute of Medicine (K.L., M.Ø., E.S.H.), University of Bergen, 5020 Bergen, Norway; Department of Medicine (K.L., E.S.H.), Haukeland University Hospital, 5021 Bergen, Norway; and Department of Psychiatry (F.A.H.), University of Cambridge, Cambridge CB2 2QQ, United Kingdom

* To whom correspondence should be addressed. E-mail: Kristian.lovas@helse-bergen.no.

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).

 

From http://jcem.endojournals.org/cgi/content/abstract/jc.2009-1711v1