Validation study of a novel approach for assessment of retronasal olfactory function with combination of odor thresholds and identification

Purpose The present study aimed to establish a test battery for the clinical assessment of retronasal odor thresholds and retronasal odor identification. Study design Prospective case-control series. Methods Sixty participants (36 women, 24 men, mean age 37.6 +/- 19.4 years) were enrolled in this study; 36 were healthy controls and 24 were patients with olfactory dysfunction. Orthonasal olfactory function was assessed with the Sniffin' Sticks test battery. Retronasal olfaction was assessed with oral odorant delivery using special containers for threshold function, and with oral tasteless powders for odor identification. Results Retronasal and orthonasal olfaction were significantly correlated for threshold scores, identification score, and the sum of threshold and identification score (TI score). Validity analyses showed that the retronasal TI score was able to discriminate between healthy controls and patients with olfactory dysfunction. Conclusions Normosmic participants can be distinctly differentiated from patients with olfactory dysfunction using a valid test battery comprised of retronasal threshold and identification tests. Based on the current findings, we advocate a TI score of 16 as a cut-off between patients and controls. Therefore, TI scores of 17 and above would indicate retronasal normosmia.

Automated summary

This study aimed to establish a test battery for clinical assessment of retronasal odor thresholds and identification, finding significant correlations between retronasal and orthonasal olfaction. The retronasal TI score can effectively differentiate between healthy controls and patients with olfactory dysfunction.