Letter to the Editor

Dear Editor,

Are loss of smell or taste being considered important symptoms for COVID-19 patients in Hong Kong?

The novel coronavirus disease (COVID-19) pandemic has led to the tragic loss of more than 963,000 lives worldwide while more than 5000 confirmed cases were identified in Hong Kong. The classical presenting symptoms such as fever, dry cough, sputum production, runny nose, sore throat and dyspnea are commonly used to screen suspected COVID-19 patients together with contact and travel history. A joint press released from the British Rhinologic Society and British Association of Otorhinolaryngology on March 21, 2020 reported that an increasing number of COVID -19 patients reported smell and taste disturbances in China, Italy, South Korea, Iran and United Kingdom.¹ Centre of Health Protection of the Department of Health of Hong Kong has included loss of taste and smell as the clinical features of Coronarvirus disease 2019 on 25 May 2020.

To estimate the prevalence and awareness of selfreported symptoms regarding COVID-19 of both the general public and healthcare workers, we designed an online questionnaire to rate the subjective importance of individual symptoms. This was sent anonymously to the general public and healthcare workers, who were asked to rate each presenting symptom reported to the attending doctors on a 10-point scale (10: most important, 1: less important). The symptoms included in the survey were nasal discharge, nasal obstruction, sore throat, fatigue, cough, sputum, shortness of breath, fever, loss of smell, loss of taste and myalgia.

Five-hundred and eighteen participants 18-80 years old completed the survey with a male to female ratio of 2:3. The majority of participants were between 51 to 65 years old (228 participants), followed by those aged from 39 to 50 years old (164 participants). Among the participants, one hundred and seventy-six participants (34%) were healthcare workers. Mann-Whitney U test was adopted to compare the distribution of ranking between health and non-health group. Significant difference was found in nasal discharge (p=0.044), sputum (p=0.019), and shortness of breath (p=0.031). Health care group has generally higher ranking in these three categories.

The three symptoms ranked most important were fever (scored 9.46 ± 1.49), shortness of breath (scored 9.34 ± 1.51) and cough (scored 8.56 ± 1.74), followed by smell disturbance (scored 8.50 ± 2.13) and taste disturbance (scored 8.45 ± 2.18) (Table 1). Nasal discharge (scored 6.11 ± 2.55) and nasal obstruction (scored 5.66 ± 2.50) were rated as least important. High correlation coefficients were found between nasal discharge and nasal obstruction (r=0.785, p< 0.05) and between smell loss and taste loss (r=0.907, p< 0.05).

In our online survey of the common symptoms reported in Hong Kong during this pandemic, 518 responders highly prioritised fever, SOB and cough, consistent with the most common presenting symptoms in large cohort studies.^2,3 Smell and taste dysfunction were rated just below the common presenting symptoms but higher than other symptoms including sore throat, nasal discharge, nasal obstruction and so forth. This result of high rating of smell and taste dysfunction during this pandemic might be explained by the recent influence of mass media campaigns on the general public in Hong Kong.

The reporting criteria in Hong Kong for a suspected COVID-19 case are fever, cough or pneumonia and close contact with any confirmed case within 14 days or a recent history of travel to pandemic area. For those suspected cases are tested for SARS-CoV-2, and positive cases are admitted to hospital for surveillance and further management. Cho et al⁴ performed a cross sectional cohort study in Hong Kong comparing 60 confirmed COVID-19 cases and 60 negative control cases. The reported smell and taste impairment incidence in COVID-19 patients were 46.7% and 45% respectively, whereas neither symptom occurred in the negative control group (p< 0.05). Comparing to Western study⁵ , the incidence of smell and taste dysfunction in COVID-19 patients were 68% and 71% respectively. It was also found that despite there is high prevalence of olfactory and gustatory dysfunction in COVID-19 patients, the severity and recovery from these symptoms have no correlations with the viral load of SARS-CoV-2.⁵ In order to prepare the fourth wave of COVID-19 outbreak in Hong Kong during winter, symptoms enquiry of smell and taste loss is specific to COVID-19 and essential to be included on top of the common flu symptoms.

In conclusion, public alertness to smell and taste impairment in this period of COVID-19 pandemic is exceedingly high as shown in our survey. Smell and taste dysfunction are sufficiently distinctive to be used for screening high-risk subjects for laboratory testing.

Yours sincerely,