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 <10 min for 84 %, 40 % expressed satisfaction that these issues were addressed. Analyses suggested a revision of the phase III hypothesized scale structure. Two items were deleted based on a high degree of item misfit, together with negative patient feedback. The remaining 15 items formed one eight-item scale named OH-QoL score, a two-item information scale, a two-item scale regarding dentures, and three single items (sticky saliva/mouth soreness/sensitivity to food/drink). Face and convergent validity and internal consistency were confirmed. Test-retest reliability (n = 60) was demonstrated as was RCA for patients undergoing chemotherapy (n = 117; p = 0.06). The resulting QLQ-OH15 discriminated between clinically distinct patient groups, e.g., low performance status vs. higher (p < 000.1), and head-and-neck cancer versus other cancers (p < 0.03). Conclusion The EORTC module QLQ-OH15 is a short, well-accepted assessment tool focusing on oral problems and QoL to improve clinical management.