[Cross-cultural adaptation and validation of a Spanish version of a specific instrument to measure health-related quality of life in patients with ankylosing spondylitis]

Abstract

Objective: To make a cross-cultural adaptation and validation of a version in Spanish of the Ankylosing Spondylitis Quality of Life Questionnaire (ASQoL) for assessing the health-related quality of life (HRQL) of patients with Ankylosing Spondylitis (AS).

Patients and methods: A cross-sectional study with test-retest. AS patients (modified New York criteria) were included. Cross-cultural adaptation was done. Construct validity was assessed comparing the ASQoL scores with the SF-36 and EuroQol scores and diseaserelated variables. Internal consistency and reliability (test-retest) were assessed. Feasibility was assessed by the time spent to complete the questionnaire and the number of items without answer. Spearman correlation coefficient, Mann-Whitney U test, and Kruskal-Wallis test were used in the statistical analysis. Cronbach́alpha coefficient and statistic kappa were used for assessing internal consistency and reliability.

Results: Fifty-four patients, 37 males (68.5%), with age (mean±SD) 40.5±10.5 years, were included. The ASQoL global score was 6.8±4.7 (median, 7; range, 0-17). The ASQoL scores had high correlations with physical (rho = 0.79) and mental (0.69) SF-36 components, the SF-36 domains pain (0.82), vitality (0.75), and role-physical (0.68), and the most of the disease-related variables. The ASQoL scores were significantly different between patients with different response levels in the health profile of the EuroQol. The Cronbach́alpha coefficient was 0.86. The reliability had kappa = 1 in 12 items and rho = 0.98. The time spent to complete the ASQoL was from 2 to 5 minutes and there only was a missing answer in one patient.

Conclusion: The Spanish ASQoL is valid, reliable, and feasible instrument for assessing the HRQL of the AS patients.