Discussions:
In the contemporary COVID-19 era, the local burden of POD increased a surprising two-fold. Thus, COVID-19-related POD has indeed caused a non-negligible threat to the quality of life of the affected, as well as the Japanese public health system. Surprisingly, 5 of 7 COVID-19 patients lacked an acute diagnosis and were later diagnosed serologically. This may reflect the local situation in Japan, which once faced a severe shortage of molecular diagnostics. Comparisons to preceding findings from the UK, also indicated that seroprevalence of the COVID-19-related impairment in the odor sensation5had relied on subjective assessment of impairment lacking quantitative data. Our findings confirmed the previously reported magnitude of an increase in the disease burden, by further using robust indices of both qualitative and quantitative features (SAOQ, OE, IO).
The intranasal trigeminal system, like the gustatory system, is now recognized as a frequent neuronal target of the SARS-CoV-26. OE, which is widely used in Japan, contains menthol as one of the 12 odorants and allows for the screening of any coexisting intranasal trigeminal dysfunction. In line with previous research, non-recognition of the cooling sensation in menthol, which is an expression of trigeminal dysfunction, rather than olfactory dysfunction, was more commonly observed in our cohort of patients with COVID-19-related POD. However, some participants reported a subjective improvement in their POD during interviews, despite inconsistent unimprovement in the OE scoring. This could be due to the patient’s difficulty in distinguishing trigeminal sensation from olfaction. Thus, assessing POD in the clinic must use pleiotropic approaches and robust measures. The prognostic value of differentiating the POD etiologies in the era of COVID-19 shall be studied further in the future.