To the Editor:
Olfactory loss as a symptom of coronavirus disease 2019 (COVID-19) has been receiving increasing attention globally, with a number of international statements including it as a key symptom of the disease.1, 2, 3, 4
In response, the emergency department (ED) at Sengkang General Hospital, a tertiary care hospital in Singapore, began actively inquiring about acute olfactory loss (hyposmia or anosmia of less than 14 days’ duration) from April 23, 2020, for all patients who presented with acute respiratory symptoms and for those who fulfilled the prevailing Ministry of Health suspect or surveillance case definition. We then performed a cohort study to evaluate the utility of acute olfactory loss as a risk-stratifying tool for COVID-19.
A chart review was performed for all patients meeting the above criteria who presented between March 23, 2020, and April 4, 2020. All patients had a COVID-19 polymerase chain reaction oropharyngeal swab performed. We excluded patients with preexisting olfactory loss and those who were unable to give a history of olfactory loss reliably (eg, those with cognitive impairment).
A total of 717 patients met these criteria, and 31 had a positive test result for COVID-19 by polymerase chain reaction (Table ). In this group, 7 (22.6%) complained of acute olfactory loss, of whom 3 (42.9%) had hyposmia and 4 (57.1%) had anosmia. One patient presented with isolated anosmia, and the rest had olfactory loss associated with other symptoms of acute upper respiratory tract infection. Of 686 patients who had a negative test result for COVID-19, 22 (3.2%) had acute olfactory loss (χ2 test; P<.05). Within this group, 8 patients (36.4%) had hyposmia, whereas 14 (63.6%) had anosmia. One patient had isolated hyposmia. Acute olfactory loss as a marker for COVID-19 had a sensitivity of 22.6% and a specificity of 96.8%. In this cohort, the positive predictive value of acute olfactory loss for COVID-19 was 24.1% and the negative predictive value was 96.5%.
Table.
Olfactory loss in patients presenting to the ED who met criteria for COVID-19 swab.
| COVID-19 Positive | COVID-19 Negative | |
|---|---|---|
| Olfactory loss | ||
| Hyposmia | 3 | 8 |
| Anosmia | 4 | 14 |
| No olfactory loss | 24 | 664 |
To the best of our knowledge, this is the first study that analyzes prospectively collected hyposmia data in a single cohort of COVID-19–positive and –negative patients. Our results echo those of other studies examining the prevalence of chemosensory dysfunction in COVID-19.5 Our study is limited by the lack of objective olfactory testing, and although self-reported olfactory ability has been found to be not completely reliable, exigencies of service in the busy ED did not permit formal olfactory assessment. Data on olfactory loss developing in patients after their initial presentation were also not captured because our study was focused on the usefulness of acute olfactory loss for COVID-19 risk stratification at the ED.
The Ministry of Health suspect case definition has since been expanded to include anosmia as of April 15, 2020. Our findings support this new inclusion and suggest that it has a strong specificity for COVID-19, making it useful as a rule-in test especially in EDs to influence cohorting and isolation decisions for which testing is unavailable or results are pending.
Footnotes
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist.
References
- 1.European Rhinologic Society Information for rhinologists on COVID-19. https://www.europeanrhinologicsociety.org/?page_id=2143 Available at:
- 2.ENT UK Advice for patients with new-onset anosmia during COVID-19 pandemic. https://www.entuk.org/advice-patients-new-onset-anosmia-during-covid-19-pandemic Available at:
- 3.French Society of ENT (SFORL) Anosmia alert: COVID-19. https://www.sforl.org/wp-content/uploads/2020/03/Alerte-anosmie-COVID-19.pdf Available at:
- 4.Mao L., Wang M., Chen S. Neurological manifestations of hospitalised patients with COVID-19 in Wuhan, China: a retrospective case series study. JAMA Neurol. 2020;77:683–690. doi: 10.1001/jamaneurol.2020.1127. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Yan C.H., Faraji F., Prajapati D.P. Association of chemosensory dysfunction and COVID-19 in patients presenting with influenza-like symptoms. Int Forum Allergy Rhinol. 2020 doi: 10.1002/alr.22579. https://doi.org/10.1002/alr.22579 [DOI] [PMC free article] [PubMed] [Google Scholar]