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

OBJECTIVES: To generate and validate at pretest level a cross-culturally adapted Portuguese version of Xerosto- mia Inventory (XI), a 11-item questionnaire designed to measure specific xerostomia rating of patients com- plaints. METHODS: 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 Sjo ̈gren syn- drome were recruited for this study. The questionnaires were administered by trained and calibrated dental doc- tors 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. RESULTS: Internal consistency and test-retest reliability were excellent (Cronbach's a = 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. CONCLUSION: The Portuguese version of the XI can be considered a reliable and valid instrument to measure patients' xerostomia symptoms.