International field testing of the psychometric properties of an EORTC quality of life module for oral health: the EORTC QLQ-OH15

Purpose This international EORTC validation study (phase IV) is aimed at testing the psychometric properties of a quality of life (QoL) module related to oral health problems in cancer patients. Methods The phase III module comprised 17 items with four hypothesized multi-item scales and three single items. In phase IV, patients with mixed cancers, in different treatment phases from 10 countries completed the EORTC QLQ-C30, the QLQ-OH module, and a debriefing interview. The hypothesized structure was tested using combinations of classical test theory and item response theory, following EORTC guidelines. Test–retest assessments and responsiveness to change analysis (RCA) were performed after 2 weeks. Results Five hundred seventy-two patients (median age 60.3, 54 % females) were analyzed. Completion took