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Meta-Analysis
. 2021 Feb;361(2):216-225.
doi: 10.1016/j.amjms.2020.09.017. Epub 2020 Nov 1.

The Association of "Loss of Smell" to COVID-19: A Systematic Review and Meta-Analysis

Muhammad Aziz  1 , Hemant Goyal  2 , Hossein Haghbin  1 , Wade M Lee-Smith  3 , Mahesh Gajendran  4 , Abhilash Perisetti  5
Affiliations
Meta-Analysis

The Association of "Loss of Smell" to COVID-19: A Systematic Review and Meta-Analysis

Muhammad Aziz et al. Am J Med Sci. 2021 Feb.

Abstract

Background: The presence of olfactory dysfunction or "loss of smell" has been reported as an atypical symptom in patients with coronavirus disease 2019 (COVID-19). We performed a systematic review and meta-analysis of the available literature to evaluate the prevalence of "loss of smell" in COVID-19 as well as its utility for prognosticating the disease severity.

Methods: An exhaustive search of the PubMed/Medline, Embase, Web of Science, Cochrane Library, LitCovid NIH, and WHO COVID-19 database was conducted through August 6th, 2020. All studies reporting the prevalence of "loss of smell" (anosmia and/or hyposmia/microsmia) in laboratory-confirmed COVID-19 patients were included. Pooled prevalence for cases (positive COVID-19 through reverse transcriptase (RT-PCR) and/or serology IgG/IgM) and controls (negative RT-PCR and/or serology) was compared, and the odds ratio (OR), 95% confidence interval (CI) and the p-value were calculated. A p-value of <0.05 was considered statistically significant.

Results: A total of 51 studies with 11074 confirmed COVID-19 patients were included. Of these, 21 studies used a control group with 3425 patients. The symptom of "loss of smell" (OR: 14.7, CI: 8.9-24.3) was significantly higher in the COVID-19 group when compared to the control group. Seven studies comparing severe COVID-19 patients with- and without "loss of smell" demonstrated favorable prognosis for patients with "loss of smell" (OR: 0.36, CI 0.27-0.48).

Conclusions: Olfactory dysfunction or "loss of smell" is a prevalent symptom in COVID-19 patients. Moreover, COVID-19 patients with "loss of smell" appear to have a milder course of the disease.

Keywords: COVID-19; Coronavirus; Loss of smell; Olfactory dysfunction; SARS-CoV-2.

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Figures

Fig 1:
Figure 1
PRISMA flow diagram.
Fig 2:
Figure 2
Forest plot demonstrating overall prevalence of “loss of smell” in COVID-19 patients.
Fig 3:
Figure 3
Forest plot comparing prevalence in COVID-19 vs control group for “loss of smell”.
Fig 4:
Figure 4
Forest plot comparing severe cases in COVID-19 group presenting with “loss of smell” to patients without “loss of smell”.
See this image and copyright information in PMC

References

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