Translation, validation, and construct reliability of a Portuguese version of the Xerostomia Inventory

Abstract

To generate and validate at pretest level a cross-culturally adapted Portuguese version of Xerostomia Inventory (XI), a 11-item questionnaire designed to measure specific xerostomia rating of patients complaints. The original English version of the XI was translated into Portuguese following the guidelines for cross-cultural adaptation of health-related quality of life measures. Thirty patients with primary Sjögren syndrome were recruited for this study. The questionnaires were administered by trained and calibrated dental doctors to each patient. XI properties were examined including reliability, internal consistency, and test-retest reliability, using Cronbach's alpha, total and inter-item correlation, and intra-class correlation coefficients (ICC), respectively. Construct validity supported by objective measurements of xerostomia intra-oral signs and salivary secretion was investigated. Alpha was set at 0.05. Informed consents and local ethical committee clearance were obtained. Internal consistency and test-retest reliability were excellent (Cronbach's α=0.9; ICC range=0.79-0.94). Scatterplot interpolation and Pearson correlation coefficient suggested the presence of a strong, negative, and significant correlation between salivation and the XI scores indicating construct validity. The Portuguese version of the XI can be considered a reliable and valid instrument to measure patients' xerostomia symptoms.