Olfactory and gustatory dysfunction in COVID‐19 patients: A meta‐analysis study

Hajikhani, Bahareh; Calcagno, Tess; Nasiri, Mohammad Javad; Jamshidi, Parnian; Dadashi, Masoud; Goudarzi, Mehdi; Eshraghi, Adrien A.; Mirsaeidi, Mehdi

COVID‐19, caused by a novel coronavirus, is a persistent global pandemic. It is crucial to examine existing reports to effectively summarize and characterize its clinical course. We used a large‐scale meta‐analysis to establish prevalence rates for loss of olfaction and gustation in COVID‐19 positive patients. PubMed/Medline, Embase, and Web of Sciences were searched for articles published until April 30, 2020. Furthermore, to avoid missing papers, more searches were carried out in the reference lists of covered studies. Articles that mentioned olfactory and/or gustatory disorder in patients with COVID–19 were included for further analysis. Articles that did not report the aforementioned information were excluded. Duplicated articles, reviews, and meta‐analysis were excluded as well. The quality of the references was assessed according to the checklist provided by JBI (Joanna Briggs Institute). We used independent extraction of data by multiple observers. The pooled frequency with 95% confidence intervals (CI) was assessed using random effect model. The main outcome measures reported were the pooled frequency of olfaction and pooled frequency of gustation disorder in patients with COVID‐19 calculated using a random effect model weighted by the study population. The 15 included studies had 3,739 participants which all had confirmed COVID–19. Olfactory and gustatory disorders were assessed and a total number of 1,354 and 1,729 were reported to have taste or smell impairment, respectively. The estimated rate of taste disorder in patients with COVID‐19 was 49.0% [95% confidence interval (CI) 34.0–64.0, I2: 96%] (Figure 2). The estimated rate of olfactory disorder in patients with COVID‐19 was 61.0% (95% CI 44.0%–75.0%). Our meta‐analysis demonstrated high rates of taste (49.0%) and smell (61.0%) disorders in patients with confirmed COVID‐19. Results increase the power of recent reports—loss of olfactory and loss of gustation should now routinely be considered in the setting of COVID‐19 infection.