Revisiting Smell and Taste Dysfunctions during COVID-19 Pandemic in Hong Kong

Background: This cross-sectional cohort study in Hong Kong aimed to revisit smell and taste symptoms in COVID-19 in Chinese population which were previously underreported in China. Methods: 120 symptomatic patients underwent testing for SARS-coronavirus 2 (SARS-CoV-2) were recruited. The clinical data of confirmed COVID-19 (n=60) and control subjects (n=60) were collected, including severity of smell and taste impairment and the cycle threshold (Ct) values from a SARS-CoV-2 polymerase chain reaction (PCR) assay of specimens. Results: Twenty-eight (46.7%) and twenty-seven (45%) COVID-19 patients reported smell and taste impairment, respectively, whereas neither symptom occurred in the control group (p < 0.05). Cough (60%), fever (50%), expectorant (43%) and dyspnea (25%) were common symptoms in COVID-19 but were not specific to the diagnosis. Conclusion: We observed no ethnic differences in COVID-19-related smell and taste dysfunctions between Chinese and Caucasians. These symptoms were more specific for COVID-19 than fever, cough, expectorant and dyspnea

and taste disturbance in COVID-19 to incidence, symptomatology, objective tests and possibly recovery in the West [5,6]. However, no case series has been reported to re-evaluate smell and taste impairment in Chinese patients with COVID-19 outside province of China, despite an apparently low incidence of these symptoms in previous large cohort studies [7][8][9].
Both the United States and European countries have reported a high incidence of smell (68-85.6%) and taste dysfunction (71-88%) among patients with COVID-19 [10,11]. In contrast, Korea reported that only 15.3% of a large cohort of patients (N = 3,191) reported a loss of smell or taste [12]. It is therefore unclear whether these symptoms are affected by ethnic differences or other geographical factors. Here, we aim to describe our preliminary evaluation of smell and taste dysfunction associated with COVID-19 through a cross-sectional cohort study of an ethnic Chinese population in Hong Kong. Future publications from Western and Asian countries will provide a comparative comprehensive overview of these specific symptoms and their potential use as specific screening tools for COVID-19.

Materials and Methods
This study adhered to the tenets of the Declaration of Helsinki.

Questionnaire Design and Data Collection
A traditional Chinese-language questionnaire was designed to collect the patients' clinical data via phone contact or online submission. Information was collected on history of rhinitis, nasal surgery, use of medication for nasal symptoms, and symptoms such as nasal discharge, nasal obstruction, purulent nasal discharge, blood-stained nasal discharge, cough, sputum, shortness of breath

Statistical analysis
All statistical analyses were performed using SPSS version 23.0 (IBM, Armonk, NY, USA). Symptom variables included in the comparisons were runny nose, nasal obstruction, blood-stained or purulent nasal discharge, cough, sputum, SOB, fever and change in smell or taste. A logistic regression analysis was used to compute the odds ratios (OR) of the symptoms. Student's t-test and Pearson's chi-square test were used to compare demographic statistics and questionnaire results between groups. The Mann-Whitney U test was used to compare smell and taste impairments between groups. The relationship between smell and taste impairments was analyzed using Spearman's rank correlation coefficient. A p value < 0.05 was considered statistically significant.

Am J Biomed Sci & Res Copy@ Peter KM Ku
In this cross-sectional study, 74 confirmed COVID-19 patients were contacted, and 60 were recruited; 14 declined to participate.
Ninety-one control patients were contacted and 60 were recruited; 30 could not be reached by phone and one declined to participate.

Patients' demographic data and presenting symptoms
The COVID-19 group comprised 36 males and 24 females, while the control group comprised 26 males and 34 females (p = 0.068).
The mean ages were 37.8 ±16.6 years in the COVID-19 group and 38.4 ± 14.2 years in the control group (p = 0.818). The two groups did not differ significantly in terms of basic demographics. The most common symptoms of COVID-19 patients were cough (60%), fever (50%) and expectorant (43%), whereas only 3 to 5% reported purulent and blood-stained nasal discharge ( Figure 1). Dyspnea and fever were more common among confirmed COVID-19 cases than among controls (25% vs 8.3%; OR 3.7, p = 0.014 and 50% vs 23.3%; OR 3.6; p = 0.002, respectively). The presence of rhinorrhea, nasal obstruction, purulent and blood-stained nasal discharge, cough, and sputum production did not differ significantly between the groups (Table 1).

Ct values of PCR assays of nasopharyngeal and throat swabs
The mean Ct value of SARS-CoV-2 PCR tests in the COVID-19 group was 27.4 ± 6.6. The Ct values of different subgroups of patients ranged from 26.7 ± 6.7 to 34.0 ± 2.9 ( Table 2). The result of one-way ANOVA did not show statistically significant relationship between the Ct value and the incidence of smell or taste dysfunctions (p = 0.822 and p = 0.228, respectively).   . All suspected cases are tested for SARS-CoV-2, and positive cases are admitted to hospital for surveillance. Although the incidence of fever, SOB, cough, and expectorant ranged from 25% to 60% among our confirmed cases, they were also present in 8 to  However, this study is strengthened by its use of a control group with symptoms, which allowed us to demonstrate a much higher prevalence of smell and taste impairment among the COVID-19 cases in Chinese population. Smell impairment could present as the earliest symptom and be the only symptom of some patients.
Moreover, assistance from our team allowed us to obtain data from more than two-thirds of the admitted COVID-19 cases at our local facility. While the daily incidence of locally confirmed COVID-19 patients is on single digit recently, it will be lingering on for some time as in some countries like China, Japan, Singapore and Korea.
Our real threat is from those asymptomatic carriers who may present lately; the imported cases from countries which are still heavily affected by this pandemic; and another potential seasonal outbreak in fall or winter. Therefore, we still need to be highly vigilant at all time about COVID-19 infection even when global situation seems to ease out in recent weeks.

Conclusion
We observed no ethnic differences in COVID-19-related smell and taste dysfunction between Chinese and Caucasians. These symptoms were more specific for COVID-19 than fever, cough, and shortness of breath. In this study, smell and taste dysfunction are sufficiently distinctive to be used for screening high-risk subjects for laboratory testing.

Funding
No funding was received for work described in or related to this study.