The Systemic Sclerosis Questionnaire (SySQ): Validation of the translation of the original German version into Spanish and its relationship to the disease and to quality of life

Abstract

Objective: Translation, transculturation and validity of the self-administered questionnaire for functionality (Systemic Sclerosis Questionnaires [SySQ]) for use in Spanish patients with systemic sclerosis and its relationship to the severity of the disease and to quality of life.

Patients and methods: We conducted an observational analytical study to perform a cross-cultural validation of the self-administered questionnaire on functionality in scleroderma. The validity of the form and content was evaluated by an expert panel. The method included: a) adaptation into Spanish of the construct for translation and back translation, and transculturation; b) internal consistency with the SySQ (Cronbach's alpha), and c) reproducibility was assessed taking into account all occasions in which the test was performed with Cohen's kappa. Additionally, we calculated the Spearman correlation coefficient with the Medsger severity scale, Health Assessment Questionnaire score and SF-36 score.

Results: We included 70 patients with systemic sclerosis: age 17-78 (51±12) years, 65 (93%) were women, diffuse/limited subtype 64/36%, disease duration of 0.5-40 years. Optimal internal consistency for all categories of the final version of SySQ (Cronbach's α of 0.961) and intraobserver reliability in 2 tests over a 2-week interval (Cohen's kappa coefficient 0.618) and optimal interobserver reliability in 2 tests on the same day (Cohen's kappa coefficient 0.911). Moderate correlation between functionality by SySQ and by Health Assessment Questionnaire (r=0.573, P<.0001). Inverse correlation between SySQ and quality of life mental health domain SF-36 (r=-0.435, P<.001) and physical domain SF-36 (r=-0.638, P<.001). Medsger severity scale (tendon, heart, lung, vascular) also showed significant correlation with SySQ.

Conclusions: SySQ in this validated Spanish version is a suitable instrument to measure functional status in patients with systemic sclerosis. Reduced functionality is related to greater tendon and peripheral vascular involvement and to a poorer quality of life.

Keywords: Calidad de vida; Esclerosis sistémica; Funcionalidad; Functionality; Quality of life; Systemic sclerosis.