The incidence of anosmia in patients with laboratory-confirmed COVID 19 infection in India: An observational study

J Anaesthesiol Clin Pharmacol. 2021 Jan-Mar;37(1):51-56. doi: 10.4103/joacp.JOACP_653_20. Epub 2021 Apr 10.


Background and aims: Acute loss of smell or anosmia is a common and sometimes the only symptom observed in patients with coronavirus disease-2019 (COVID-19). The objective of the study was to determine the prevalence, time of onset, and duration of anosmia in patients with COVID-19 infection and the association of anosmia with other symptoms and eosinophil count.

Material and methods: Two hundred patients with laboratory-confirmed COVID-19 infection, who were asymptomatic or mildly symptomatic were assessed for olfaction with a nonirritant odor. The presence of anosmia was recorded, and a questionnaire integrating the anosmia reporting tool was filled. Patients with anosmia/hyposmia were followed telephonically at 7 and 14 days for resolution of anosmia and other symptoms. The presence of anosmia was correlated with eosinophil count.

Results: Of the 200 COVID-19 patients, 87% were symptomatic. More than half of the patients had fever (56%). Anosmia was observed in 30% of the patients and hyposmia in 4% of patients. In 41% of the patients, olfactory loss was reported before diagnosis. The mean duration of anosmia was 7.8 (± 5) days; 97% of patients recovered with a resolution of symptoms within 2 weeks. Ageusia was the most commonly and significantly associated symptom with anosmia (66%, n = 45) followed by sore throat (41%), and rhinorrhea (28%). The symptoms in both the sexes were comparable. Absolute eosinophil count of <40/μL was observed in 59 patients (29.5%) and an absolute eosinophil count of 0 in 17 patients (8.5%). Among the 68 anosmic patients, 36 (47%) patients had eosinopenia, which was statistically significant.

Conclusion: Anosmia is an early and sometimes the only symptom in approximately one-third of the patients with COVID-19 infection. Eosinophil count should be checked in anosomic patient with suspicion of COVID-19 infection. Objective tools for olfactory and gustatory assessment should be brought into practice for early and prompt diagnosis to control the spread of the disease.

Keywords: Ageusia; COVID-19; anosmia; anosmia reporting tool; eosinophil count.