Development of a quality-of-life instrument for autoimmune bullous disease: the Autoimmune Bullous Disease Quality of Life questionnaire.

IMPORTANCE Quality-of-life (QOL) evaluation is an increasingly important outcome measure in dermatology, with disease-specific QOL instruments being the most sensitive to changes in disease status. OBJECTIVE To develop a QOL instrument specific to autoimmune bullous disease (AIBD). DESIGN A comprehensive item generation process was used to build a 45-item pilot Autoimmune Bullous Disease Quality of Life (ABQOL) questionnaire, distributed to 70 patients with AIBD. Experts in bullous disease refined the pilot ABQOL before factor analysis was performed to yield the final ABQOL questionnaire of 17 questions. We evaluated validity and reliability across a range of indices. SETTING Australian dermatology outpatient clinics and private dermatology practices. PATIENTS AND EXPOSURE: Patients with a histological diagnosis of AIBD. MAIN OUTCOMES AND MEASURES The development of an AIBD-specific QOL instrument. RESULTS Face and content validity were established through the comprehensive patient interview process and expert review. In terms of convergent validity, the ABQOL was found to have a moderate correlation with scores on the Dermatology Life Quality Index (R = 0.63) and the General Health subscale of the 36-Item Short Form Health Survey (R = 0.69; P = .009) and low correlation with the Pemphigus Disease Area Index (R = 0.42) and Autoimmune Bullous Disease Skin Disorder Intensity Score (R = 0.48). In terms of discriminant validity, the ABQOL was found to be more sensitive than the Dermatology Life Quality Index (P = .02). The ABQOL was also found to be a reliable instrument evaluated by internal consistency (Cronbach α coefficient, 0.84) and test-retest reliability (mean percentage variation, 0.92). CONCLUSIONS AND RELEVANCE The ABQOL has been shown to be a valid and reliable instrument that may serve as an end point in clinical trials. Future work should include incorporating patient weighting on questions to further increase content validity and translation of the measure to other languages. CLINICAL TRIAL REGISTRATION anzctr.org.au Identifier: ACTRN12612000750886.