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.