COVID-19: Anosmia Predictive of Less Severe Infection

coronavirus, covid19
Current guidelines from Italy, the UK, and China do not focus on screening patients for anosmia as a potential symptom for COVID-19.

Loss of smell is an independent positive prognostic factor of a less severe coronavirus disease 2019 (COVID-19) infection, according to a study published in the Annals of Allergy, Asthma and Immunology.

COVID-19 can present with various symptoms. Currently, guidelines from Italy, the United Kingdom, and China focus on screening patients for symptoms of fever and cough and exclude anosmia. However, the reported symptom of loss of smell has been associated with a greater likelihood of positive COVID-19 infection than any other symptom of an upper respiratory infection. As more is learned about COVID-19, the relative predictive value of COVID-19 symptoms is under investigation. Therefore, researchers sought to ascertain the role of smell loss in risk stratification and prediction of COVID-19 prognosis.

In total, 1013 people with COVID-19 were identified by an electronic medical records query and included in the study. Data, including demographic variables, clinical characteristics, COVID-19 symptoms and treatments, and clinical evaluations, were retrieved. Patients were evaluated using a pre-designed COVID-19 screening questionnaire and were asked about their symptoms, including whether they experienced acute loss of smell. Additionally, history data were retrieved and included patient demographics, body mass index, comorbid conditions, pre-existing smell dysfunction, and COVID-19-related inflammatory laboratory values. To calculate the odds ratio (OR) of loss of smell in association with nominal dependent variables and COVID-19 outcome, logistic regression was used.

Results demonstrated that anosmia was an independent positive prognostic factor of less severe COVID-19. Of the included patients, 20.9% of patients reported loss of smell during their initial COVID-19 evaluation. When compared with patients without anosmia, patients with loss of smell were younger (aged 46 vs 49 years; P =.02), more likely to be women (64.7% vs 52.8%; P =.003), and had a higher body mass index (33.6 vs 31.5; P =.001).

Additionally, when compared with patients without anosmia, there were significant associations between loss of smell and history of pre-existing smell dysfunction (OR, 4.66; 95% CI, 2.07-10.46), allergic rhinitis (OR, 1.79; 95% CI, 1.12-2.87), and chronic rhinosinusitis (OR, 3.70; 95% CI, 1.29-10.67). When compared with patients without smell loss, patients with smell loss showed less lymphopenia and higher albumin counts (P =.001 and P =.02, respectively).

Finally, loss of smell was also significantly associated with decreased hospitalization (OR, 0.69; 95% CI, 0.47-0.99), intensive care unit admission (OR, 0.38; 95% CI, 0.30-0.70), intubation (OR, 0.43; 0.21-0.89), and acute respiratory distress syndrome (OR, 0.45; 95% CI, 0.23-0.89) when compared with patients without loss of smell.

The primary study limitations were its retrospective nature, the subjective nature of smell loss, and the focused nature of the data collection.

“Our data implicates smell loss as an independent positive prognostic factor of a less severe COVID-19 infection,” the researchers concluded.


Foster KJ, Jauregui E, Tajudeen B, Bishehsari F, Mahdavinia M. Smell loss is a prognostic factor for lower severity of COVID-19 [published online July 24, 2020]. Ann Allergy Asthma Immunol. doi:10.1016/j.anai.2020.07.023