Factor analysis of the questionnaire of olfactory disorders in patients with chronic rhinosinusitis.

Background: Olfactory-specific quality of life (QOL) can be measured using the Questionnaire of Olfactory Disorders-Negative Statements (QOD-NS), which examines various aspects of olfactory dysfunction. It is unknown if certain factors of the QOD-NS differentially impact QOL.
Methods: Patients with chronic rhinosinusitis (CRS) completed the QOD-NS, 22-item Sino-Nasal Outcome Test (SNOT-22), Medical Outcomes Study Short Form 6-D (SF-6D) health utility measure, and Patient Health Questionnaire-2 (PHQ-2) depression screen. Exploratory factor analysis of the QOD-NS was performed. Associations between QOD-NS factors and other QOL metrics were analyzed before and after endoscopic sinus surgery (ESS).
Results: Outcomes were examined on 132 patients. The QOD-NS contains 4 distinct factors. There was no difference in associations between the different factors and baseline clinical characteristics. ESS had greatest effect size (d) on factors 2 and 4 (d = 0.29 and 0.27, respectively, p < 0.05). Postsurgical changes in the SF-6D and SNOT-22 had the strongest correlation with factor 2 scores (r = 0.29 and 0.34, respectively, p < 0.05), and changes in the PHQ-2 had the strongest correlation to factor 3 (r = 0.24, p < 0.05). Abnormal QOD-NS scores at baseline were associated with effect size increases of 50% to 100% (p < 0.05).
Conclusion: The QOD-NS measures 4 distinct factors. Eating-related questions had the greatest improvement after ESS. Health utility and CRS-specific QOL improvement most strongly associated with factor 2, while PHQ-2 changes are most highly associated with factor 3, suggesting a differential impact of the factors of the QOD-NS on varying aspects of QOL.
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