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Retronasal Olfactory Test May Differentiate Normosmic and Hyposmic Patients

by Linda Kossoff •

How do newly generated data of retronasal olfactory threshold values for normosmic and hyposmic individuals hold up after the discriminative power for normosmic/hyposmic differentiation is determined?

BOTTOM LINE

The retronasal olfactory test, a psychophysical odor test performed using an orally presented stimulus, can be used to differentiate normosmic and hyposmic cases.

BACKGROUND: Odor stimuli travel via the orthonasal pathway (inspiratory air through nostrils) and retronasal pathway (active factors in the oral cavity). The lowest odorant amount needed for an olfactory receptor response is the olfactory threshold. Decreases in sense of smell affect orthonasal and retronasal odor thresholds and are used to diagnose olfactory loss.

STUDY DESIGN: Prospective, descriptive, and methodological study.

SETTING: Department of Otolaryngology, Dokuz Eylül University School of Medicine, Izmir, Turkey.

SYNOPSIS: Researchers evaluated the orthonasal olfactory function of 20 normosmic (nine women, 11 men, mean age 26.25) and 20 hyposmic (13 women, seven men, mean age 35.15) patients using the Sniffin’ Sticks test, and recorded odor threshold, discrimination, and identification values and threshold discrimination identification (TDI) scores. To determine cutoff values, they administered a 13-item test battery for retronasal olfactory threshold using a solution of 2:1 diluted phenylethyl alcohol (PEA). The retronasal olfactory threshold was determined as four consecutive correct answers. The researchers then compared test threshold, discrimination, identification, TDI scores, and retronasal threshold values of normosmic cases and hyposmic cases and found normosmic group scores to be significantly higher after controlling for age. Results showed that the retronasal olfaction thresholds of PEA can successfully distinguish the normosmic and hyposmic individuals at a cutoff value of 8.5, with sensitivity and specificity values of 95% and 100%, respectively. Authors concluded that this test can be used to successfully differentiate normosmic and hyposmic cases. Study limitations included potential altering effects of patients’ tongue movements during the protocol, and taste limitations of PEA in an aqueous solution.

CITATION: Özay H, Çetin AC, Ecevit MC. Determination of retronasal olfactory threshold values. Laryngoscope. 2021; 131:1608-1614