Abstract
The Questionnaire of Olfactory Disorders-Negative Statements (QOD-NS) is a 17-item instrument measuring olfactory-specific quality of life (QOL). However, in clinical research patients can be overwhelmed with multiple questionnaires. We recently developed the 7-item brief QOD-NS (B-QOD). Our objective was to evaluate the psychometric properties of the B-QOD in both the development (D) sample, and in a separate replication (R) sample. Testing on D (n=203) and R (n=281) samples included initial exploratory factor analysis (EFA), followed by internal reliability, information loss, and confirmatory factor analysis (CFA). Finally, incremental predictive utility analysis (IPUA) was performed by correlating the B-QOD with the 22-item Sino-Nasal Outcome Test (SNOT-22) survey. EFAs of both D and R demonstrated an underlying single-factor structure (eigenvalue=4.17 and 3.57, respectively) with comparable loading factors (R>0.30 for both). B-QOD also had good internal reliability in both D and R (Cronbach's alpha=0.88 and 0.83, respectively). Also, there is minimal information loss with B-QOD compared to QOD-NS in both D and R (R=0.98 and 0.96, respectively). CFA indicates that the B-QOD single-factor model has good overall fit as measured by the Comparative Fit Index (CFI) and the Standardized Root Mean Squared Residuals (SRMSR) in the D and R samples (CFI=0.99 and 0.97; SRMSR=0.035 and 0.053). IPUA shows that the QOD-NS offers no additional predictive benefit of SNOT-22 scores when compared with B-QOD. The 7-item B-QOD captures a structurally coherent and reliable single dimension, with minimal information loss and excellent external predictive utility when compared to the QOD-NS.
Highlights
IntroductionChronic rhinosinusitis (CRS) is a common inflammatory disorder affecting ∼5% to 16% of North American populations.[1] Symptoms of CRS are nasal congestion, discolored nasal drainage, facial pain/pressure, and olfactory dysfunction (OD), with OD estimated to affect between 40% and 80% of CRS patients in certain study populations.[2] OD ranks as the second most important symptom for CRS patients after nasal congestion,[3] and has garnered significant attention in quality of life (QOL) and outcomes research
SUBJECTS AND METHODSChronic rhinosinusitis (CRS) is a common inflammatory disorder affecting ∼5% to 16% of North American populations.[1]
We present standardized factor loadings, which estimate the correlation between the underlying factor and the items; residual variances estimate the variance in item scores not attributable to the underlying factor
Summary
Chronic rhinosinusitis (CRS) is a common inflammatory disorder affecting ∼5% to 16% of North American populations.[1] Symptoms of CRS are nasal congestion, discolored nasal drainage, facial pain/pressure, and olfactory dysfunction (OD), with OD estimated to affect between 40% and 80% of CRS patients in certain study populations.[2] OD ranks as the second most important symptom for CRS patients after nasal congestion,[3] and has garnered significant attention in quality of life (QOL) and outcomes research This has led to the development of instruments that focus on olfactory-specific QOL.[4,5,6] In particular, the questionnaire of olfactory disorders negative statements (QOD-NS) is a 17-item validated instrument in the measurement of olfactory-specific QOL, and demonstrates robust psychometric properties.[7,8].
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