2.2 Olfactory and gustatory function test
All patients underwent a psychophysical olfactory function test, the YSK
olfactory function test (YOF) (RHICO Medical Co., Seoul, South Korea).
The YOF test is a validated conventional psychophysical olfactory
function test composed of three subsets: threshold, discrimination, and
identification. The YOF test was performed following the manufacturer’s
instructions. The threshold-discrimination-identification (TDI) score
range from 1 to 36, and the participants’ olfactory function outcomes
were labeled as normosmia, hyposmia, or anosmia based on the previously
reported criteria.13
The gustatory function test, which was developed and validated for use
with Korean populations, was applied.14 Briefly, the
testing protocol consisted of 30 taste solutions (six concentrations of
each of the five tastants: sweet (sucrose with a concentration ranging
from 0.0048 to 0.1563 g/mL), bitter (quinine hydrochloride;
0.00005–0.0016 g/mL), salty (sodium chloride; 0.0006–0.0192 g/mL),
sour (citric acid; 0.0002425–0.00781 g/mL), and umami (monosodium
glutamate; 0.002–0.064 g/mL). A single drop (approximately 40 µL) of
the taste solution was applied to the middle part of the anterior
one-third of the tongue, and between the drops, the patients were told
to rinse their mouths with tap water. The ‘taste score,’ used to
evaluate the overall gustatory function, was the sum of the correctly
recognized taste thresholds. Patients with a recognition taste score of
less than 12 were regarded as having impaired gustatory
function.14
The subjective questionnaires regarding chemosensory function were
obtained on their first visits.