Chemosensory Dysfunction in Long-Term COVID-19 Assessed by Self-Reported and Direct Psychophysical Methods

Abstract

Chemosensory dysfunction is a frequent postacute sequela of COVID-19. Depending on the type of test used to measure it (self-report vs. direct test), the degree of chemosensory dysfunction in long-term COVID-19 has been found to be highly variable. In this manuscript, we report the cross-sectional data (first assessment) of a longitudinal study (6-month follow-up) examining smell, taste, and chemesthesis in participants affected by long-term COVID-19 (COVID+) and participants without COVID-19 (COVID-) by means of both self-reported and direct psychophysical methods. In total, 208 Italian participants (COVID+ n = 133; COVID- n = 75) completed the Smell and Taste Check developed by the Global Consortium for Chemosensory Research (GCCR), which includes self-reports on smell, taste, and chemesthetic abilities as well as direct intensity ratings of unstandardized smell, taste, and chemesthetic household items. Furthermore, all participants completed SCENTinel, a validated direct smell test. We found a positive association between the self-reported, unstandardized direct test and the validated direct test for smell, indicating moderate to large agreement across measures. Furthermore, the performance on SCENTinel was significantly associated with self-reported smell loss. A positive association between the self-reports and the intensity of household items was also retrieved for taste and chemesthesis. The time relative to COVID-19 onset (267.3 ± 113.9 days) did not modulate the chemosensory performance of self-reported abilities, intensity ratings, and SCENTinel. All in all, we confirm the impairment of three chemical senses (smell, taste, and chemesthesis) in an independent sample of Italian participants affected by long-term COVID-19 by using and comparing self-reported and direct psychophysical methods. We contribute to the discussion on best practices to monitor chemosensory dysfunction in individuals affected by long-term COVID-19.

Keywords: COVID-19; chemesthesis; chemosensory dysfunction; smell; taste.

Figure 1

Split violin plots for the GCCR Smell and Taste Check outcomes by COVID-19 status: (a) chemosensory abilities and (b) the experienced intensity of household items. The horizontal thick line within the boxes represents the mean. The lower and upper horizontal lines indicate the 25th and 75th percentiles of the distribution, respectively (i.e., interquartile range). The whiskers indicate the minimum and maximum values located in a range 1.5 times greater than the interquartile range. The shaded area surrounding each box depicts a rotated kernel density plot.

Figure 2

The association (Spearman’s rho) between self-reported smell, taste, and chemesthesis abilities (GCCR ability) and the intensity of unstandardized household smell, taste, and chemesthetic items (GCCR intensity) in (a) the COVID+ group (n = 109) and (b) the COVID− group (n = 73).

Figure 3

The association (Spearman’s rho) between the intensity of a calibrated odor stimulus (SCENTinel intensity), the intensity of unstandardized household smell items (GCCR intensity), and self-reported smell ability (GCCR ability) in (a) the COVID+ group (n = 109) and (b) the COVID− group (n = 73).