Degrees of xerostomia? A Rasch analysis of the Xerostomia Inventory.

The current study expanded the evidence on the XI and SXI validity and provides new implications for practice: a 3-point categorization ("Never," "Occasionally" and "Very often") should be preferred rather than the original 5-point categorization; the XI and SXI scores can be compared between men and women and will reflect true differences in xerostomia rather than measurement bias.