Results
Cohort
Between March 2020 and March 2021, 20 healthy volunteers were included in the study. Characteristics of the volunteers are described in Table 1.
Sniffin’ Stick Test
Intra-group comparison
In group 1 and 2, all the subjects were normosmic without a mask, except for two subjects who were hyposmic (Table 2). The two hyposmic subjects (respectively 49 and 52 years old) had a TDI of 28.5 for subject 1 and 27.5 for subject 2.
All the subjects, except one, experienced a significant decreased olfactory performance when wearing a mask (p=0.02) (Figure 1).
The average difference observed with and without a mask were inferior to 5 for both group 1 and 2 (respectively 3.77 and 4.87), being non-clinically relevant. Nevertheless, 8 participants (40%, 35±13 years old) had a TDI difference with and without a mask superior to 5. Among them, four participants (one in group 1 and 3 in group 2, 38±19 years old) were normosmic without a mask (TDI superior to 30.5, average TDI of 34.9±1.1), while being recategorized as hyposmic with a mask (TDI inferior to 30, average TDI of 27.8±0.6). For the 4 other participants with a TDI difference with and without mask superior to 5 (average TDI difference of 6.25±1.2, 33±6 years old), they were normosmic with and without a mask: average TDI of 35.3±1.6 and 41.6±1.1 respectively.
The identification test appeared to be the less impacted sub-test when wearing a mask (Table 2). The difference in threshold tests with and without a mask was greater in group 2 than in group 1 (2,08 and 1,48 respectively), but without clinically impact (difference in T-score<2.5). The difference in discrimination test with and without a mask was greater in group 2 than in group 1 (3,3 and 1,9 respectively), with only clinical significance in group 2 (difference in D-score>3).
Inter-group comparison
The differences in average total scores between group 1 and 2 were compared using a Mann Whitney Test and were not statistically significant (p=0.57).