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Further testing of the xerostomia inventory
1Department of Oral Health, School of Dentistry, The University of Otago, Dunedin, New Zealand. mthomson@gandalf.otago.ac.nz
Objective:
To examine the concurrent validity and temporal stability of the xerostomia inventory (XI), an 11-item summated rating scale that was developed to enable measurement of the severity of dry mouth symptoms in epidemiologic and clinical studies.
Study Design:
A prospective cohort study design was used. Measurements of the severity of dry-mouth symptoms were made with the use of the XI and a standard dry-mouth question ("How often does your mouth feel dry?") on 2 groups 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 patients 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 older individuals who were not expected to undergo changes in mouth dryness over 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 higher among the onset group. The mean XI scores of the normal group did not differ over the observation period, indicating acceptable temporal stability of the XI. The scores of the onset group showed a substantial increase between baseline and 2 months, after which the 2-month level was sustained over 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 regression was used to estimate the difference between the final scores after adjusting for age, sex, and initial difference in scores between the 2 groups. This was found to be 9.17 (95% CI 6.24, 12.10) and confirmed that undergoing 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 method for measuring the severity of the symptoms of dry mouth in clinical and epidemiologic studies.