Long COVID-19 olfactory dysfunction: discrepancy between psychophysical tests and self-perception

To evaluate the discrepancies between psychophysical olfactory tests and self-perceived smell function in consecutive patients with long COVID-19-related olfactory dysfunction, and to compare the characteristics of this impairment with those observed in other nasal conditions, in order to improve diagnostic accuracy and guide targeted treatment strategies.

An observational study of 86 long COVID-19 patients assessed by the Barcelona Smell Test (BAST-24 Plus), Visual Analogue Scale (VAS), and the quality-of-life Sino-Nasal Outcome Test (SNOT-22). Results were compared with 120 healthy controls and 121 patients with chronic rhinosinusitis with Nasal Polyps (CRSwNP).

Long COVID-19 patients reported a mean VAS score of 6.34 and a SNOT-22 score of 26.43, with question 21 (smell) accounting for 12.67% of the total. No correlation was found between VAS and total SNOT-22 score, but a moderate positive correlation was observed with question 21 (r = 0.488, p < 0.001). BAST-24 Plus scores were significantly lower than in controls for Detection, Identification, and Correct Answer (p < 0.001). Compared to the CRSwNP group, long COVID-19 patients showed less impairment in Detection and Identification (p < 0.001). A stronger negative correlation was observed between VAS and Identification (r = -0.629, p < 0.0001) than with Detection (r = -0.482, p < 0.0001), suggesting that odor identification dysfunction has a greater impact on subjective perception.

The subjective perception of olfactory dysfunction does not correlate with psychophysical test results in long COVID-19 patients and is characterized by a predominantly identification-dominant quantitative impairment, which differs from other disorders showing detection-dominant impairment. These findings highlight the need for specific diagnostic and therapeutic strategies.

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