COVID-19 could be suspected when patients report severe reduction of taste and smell in the absence of nasal obstruction, according to a study which says the findings can help general physicians identify and quarantine potential infected individuals before confirmation of diagnosis.

In the study, published in the journal JAMA Otolaryngology Head & Neck Surgery, scientists surveyed 204 COVID-19 patients and found that taste reduction was present in 55 per cent of them, whereas smell reduction was observed in about 41 per cent of the people.

Based on the results of the survey, the researchers, including those from Humanitas University in Italy, said the reduction of taste and/or smell may be a frequent and early symptom of COVID-19.

The telephone survey study investigated patients diagnosed with COVID-19 from March 5 to March 23, 2020, who were hospitalised or discharged from a medical centre.

It said the patients who were unable to answer — intubated, receiving noninvasive ventilation, or deceased, or unreachable by telephone — were excluded from the study.

“Of 359 consecutive patients, 204 fulfilled the inclusion criteria, 76 were unable to answer, 76 were unreachable by telephone, and three refused,” the scientists noted in the study.

The study said 116 patients reported reduction of taste and/or smell, while 113 participants noted they had taste reduction and 85 with smell reduction.

“Severe reduction of taste was present in 81 patients (39.7 per cent), and severe reduction of smell was present in 72 patients (35.3 per cent),” the scientists noted in the study.

They said only 12 patients with severe taste reduction, and 12 patients with severe smell reduction reported severe nasal obstruction.

The researchers said severe reduction of taste and smell was more prevalent in female patients than in male patients, and in middle aged individuals more than in young people.

“Our results showed a significant difference between reduction of taste and/or smell compared with the other sinonasal manifestations,” the study noted.

Citing the limitations of the study, the scientists said the symptoms were self-reported, adding that further research involving more objective assessment of the patients for loss of smell and taste sensations may help validate the current findings.

From the research, they believe general practitioners may play a major role in identifying potential COVID-19 cases at an early stage when taste or smell alterations manifest, and in suggesting quarantine for such patients before confirmation or exclusion of the diagnosis.