J Korean Med Sci.  2021 Feb;36(6):e34. 10.3346/jkms.2021.36.e34.

Validation of Olfactory Questionnaire in Koreans: an Alternative for Conventional Psychophysical Olfactory Tests

• Kim JW
• Kim Hs
• Kim M
• Kim SH
• Cho SW
• Kim JY

• KMID: 2512629
• DOI: http://doi.org/10.3346/jkms.2021.36.e34

Abstract

Background
The patients with coronavirus disease 2019 (COVID-19), a worldwide pandemic infection, frequently complain of olfactory disorders. However, psychophysical olfactory tests performed by an examiner are very difficult in these highly infectious patients. This study aimed to develop and validate a questionnaire for olfactory function that can be readily used to evaluate olfactory loss.
Methods
Fourteen smell-related questions were created based on smells familiar to Koreans. Among them, questions with a κ value of 0.6 or higher were finally selected through a test-retest reliability analysis. The correlations between the scores of the olfactory questionnaire and those of olfactory function tests (Butanol Threshold Test [BTT] and Cross Cultural Smell Identification Test [CCSIT]) were analyzed. To evaluate the predictive ability of the questionnaire and elicit cutoff values, receiver operating characteristic (ROC) curves were generated.
Results
Out of the 14 questions in the questionnaire, 11 (κ > 0.6) were selected for the olfactory questionnaire. We analyzed 2,273 subjects, and there was a significant correlation between the total score of the olfactory questionnaire and the BTT (r = 0.643, P < 0.001) or CCSIT (r = 0.615, P < 0.001) scores. ROC curves for the olfactory questionnaire, BTT, and CCSIT all demonstrated high predictive power to discriminate anosmia and severe hyposmia from normosmia. Regarding mild to moderate hyposmia, however, ROC curve for the olfactory questionnaire alone showed high predictive power of discrimination from normosmia. Based on the results of ROC curves among the subclasses, we suggest the classification of the total score of the questionnaire as 0–4, 5–17, 18–27, 28–41, and 42–44, for anosmia, severe hyposmia, moderate hyposmia, mild hyposmia, and normosmia, respectively.
Conclusion
The total scores of the questionnaires correlated with the BTT and CCSIT scores. The symptom questionnaire for olfactory dysfunction may be useful as an alternative tool for olfactory function testing, when unavailable.

Keyword

Smell; Olfaction Disorders; Surveys and Questionnaires; Sensation; Anosmia

Figure

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  Fig. 1 Correlation between total score of the verified questionnaire and (A) the BTT score and (B) CCSIT score.BTT = Butanol Threshold Test, CCSIT = Cross Cultural Smell Identification Test.

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  Fig. 2 ROC curves for the total score of the olfactory questionnaire, BTT and CCSIT scores to predict the four levels of olfactory dysfunction from normosmia: (A) anosmia, (B) severe hyposmia, (C) moderate hyposmia, and (D) mild hyposmia. The self-rating scale for olfactory dysfunction is used as a reference. The predictive ability is calculated based on the AUC.ROC = receiver operating characteristic, BTT = Butanol Threshold Test, CCSIT = Cross Cultural Smell Identification Test, AUC = area under the curve.

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