Further testing of the xerostomia inventory

Objective. To examine the concurrent validity and temporal stability of the xerostomia inventory (XI), an Ii-item summated rating scale that was devel oped to enable measurement of the severity of dry mouth symptoms in epidemi ologic and clinical studies. Study design. A prospective cohort study design was used. Measurements of t he severity of dry-mouth symptoms were made with the use of the XI and a st andard dry-mouth question ("How often does your mouth feel dry?") on 2 grou ps of people at baseline, 2, 4, and 6 months. The 2 groups were chosen for their differing symptom trajectories: the Onset group (N = 57) comprised pa tients who were about to undergo radiotherapy for head and neck cancer; and the Normal group (N = 55) was a convenience sample of middle-aged and olde r individuals who were not expected to undergo changes in mouth dryness ove r the study period. Results. The sex distributions of the 2 groups were similar, but the Onset group was younger than the Normal group overall. Baseline XI scores were hi gher among the Onset group. The mean XI scores of the Normal group did not differ over the observation period, indicating acceptable temporal stabilit y of the XI. The scores of the Onset group showed a substantial increase be tween baseline and 2 months, after which the 2-month level was sustained ov er the remainder of the study period. That these patterns were mirrored in the percentage responding "Frequently" or "Always" to the standard question provided further evidence for the concurrent validity of the XI. Linear re gression was used to estimate the difference between the final scores after adjusting for age, sex, and initial difference in scores between the 2 gro ups. This was found to be 9.17 (95% CI 6.24, 12.10) and confirmed that unde rgoing radiotherapy for head/neck cancer was associated with a substantial increase in the severity of xerostomia symptoms. Conclusion. The xerostomia inventory appears to be a valid multi-item metho d for measuring the severity of the symptoms of dry mouth in clinical and e pidemiologic studies.