Materials and methods
We followed STROBE guidelines for this monocentric prospective
comparative study. Participants were randomly assigned following simple
randomization procedures (computerized random numbers) to 1 of 2
crossover groups: group 1 first performed SST with a surgical mask and
then one week later performed SST without a mask, while group 2 first
performed SST without a surgical mask and then one week later performed
SST with a mask.
Ethical approval was granted by the local Ethics Committee (Agreement
2021-01-02). Written informed consent was obtained from all individual
participants.
All the participants in this study were medical doctors and students
from an academic oto-rhino-laryngology department. The inclusion
criteria were, on a voluntary basis: sense of smell considered as normal
without a mask (subjective self-reporting); informed consent and
non-opposition were obtained. An earlier 48-hour negative Reverse
Transcriptase Polymerase Chain Reaction (RT-PCR) for the SARS-CoV-2 on
nasopharyngeal swabs was needed.
The exclusion criteria were a history of chronic or acute rhinosinusitis
disease, history of craniofacial trauma, history of radio or
chemotherapy of the head and neck sphere, symptomatology consistent with
SARS-CoV-2 one month or less before the test or recent contact case.
Before each test, patients responded to a questionnaire containing their
personal and medical history, including nasosinusal and olfactory
symptoms. Face masks used were surgical masks NF EN 14683.
The SST consisted in smelling pens blindly, with odorant pens placed for
3-4 seconds within 2cm of the nostrils (5). It was divided into three
sub-tests: a threshold test (T), a discrimination test (D) and an
identification test (I), each with a score of 16, and therefore a total
score of 48 (TDI). According to TDI, patients were considered as
normosmic (TDI>30.5), anosmic (TDI<16.5) or
hyposmic (TDI between 16.5 and 30.5) (5). The score was calculated by a
software called Olaf ®.
Statistical tests were performed using the IBM SPSS Statistics 20.
Continuous values were expressed with their average number ± Standard
Deviation (SD) and categorical values as numbers and percentages. The
intra-group results with and without masks were compared using a paired
non-parametric test. A significant difference was considered for
p<0.05.
Average results for each test and each sub-test were calculated. 60% of
subjects with TDI change of 5.5 or more will report clinical olfactory
change, so a difference in TDI scores with and without a mask less or
equal to 5 was considered as not clinically relevant (6). Differences in
T, D and I scores with and without a mask were considered of clinical
significance when superior to 2.5, 3, and 3, respectively (6).
The inter-group results were compared with a Mann Whitney test.