Systematic Review and Meta‐analysis of Smell and Taste Disorders in COVID‐19

Abstract

Objective Loss of smell and taste are considered potential discriminatory symptoms indicating triaging for coronavirus disease 2019 (COVID-19) and early case identification. However, the estimated prevalence essential to guide public health policy varies in published literature. This meta-analysis aimed to estimate prevalence of smell and taste loss among COVID-19 patients. Data Sources We conducted systematic searches of PubMed, Embase, Web of Science, and Google Scholar databases for studies published on the prevalence of smell and taste loss in COVID-19 patients. Review Methods Two authors extracted data on study characteristics and the prevalence of smell and taste loss. Random-effects modeling was used to estimate pooled prevalence. Subgroup analysis and meta-regression were conducted to explore potential heterogeneity sources. This study used PRISMA and MOOSE guidelines. Results Twenty-seven of 32 studies reported a prevalence of loss of smell, taste, or both from a combined sample of 20,451 COVID-19 patients. The estimated global pooled prevalence of loss of smell among 19,424 COVID-19 patients from 27 studies was 48.47% (95% CI, 33.78%-63.29%). Loss of taste was reported in 20 studies and 8001 patients with an estimated pooled prevalence of 41.47% (95% CI, 3.13%-31.03%), while 13 studies that reported combined loss of smell and taste in 5977 COVID-19 patients indicated a pooled prevalence of 35.04% (95% CI, 22.03%-49.26%). Conclusions The prevalence of smell and taste loss among COVID-19 patients was high globally, and regional differences supported the relevance of these symptoms as important markers. Health workers must consider them as suspicion indices for empirical diagnosis of severe acute respiratory syndrome coronavirus 2 infection.

Medical vulnerability of individuals with Down syndrome to severe COVID-19–data from the Trisomy 21 Research Society and the UK ISARIC4C survey

“…This highlights the importance of including data from community-dwelling individuals with COVID-19 in addition to routine hospital reports as hospital reports are less likely to capture mild signs and symptoms that might be important for early detection of disease. Loss of smell or taste was reported in less than 10% of individuals with DS, which was similar to the numbers reported in individuals without DS from the ISARIC4C survey, but much lower than the prevalence reported by other studies (48% loss of smell and 41% loss of taste as summarized in reference [27] ). The most likely explanation for these differences to more recent studies is that most T21RS and ISARIC4C cases were reported during the first wave of the pandemic, when we had very little knowledge about the variety of COVID-19 symptoms leading to an underdiagnosis of smell and taste disorders.…”

Clinical Characteristics, Diagnosis, and Treatment of Major Coronavirus Outbreaks

“…Recently more symptoms are being reported like loss of smell and taste sensation (132). A meta-analysis of 27 studies showed a pooled prevalence of loss of smell and taste in these patients to be 41.47% (95% Cl 3.13-31.03%) and 35.04% (95% Cl 22.03-49.26%), respectively (133). Both of these symptoms presented in patients on average on the fourth day after initial symptoms of the disease, but 13-15.5% of patients had a loss of smell and taste sensation as the first symptom (134,135).…”

Case Report: A 73-year-old suspected COVID-19 patient with severe dyspnea fully recovers after reciting nine true words from Falun Gong

“…This patient had typical symptoms of COVID-19 that included fever, taste impairment, whole body pains, and severe breathing difficulties during 15 days since the symptom onset. The prevalence of smell and taste loss among COVID-19 patients has been found to be high globally (41% to 48%); hence health workers must consider the loss of smell and taste as suspicion indices for empirical diagnosis of SARS-CoV-2 infection 9,10 . In this case report, the patient's featured symptoms supported the diagnosis of a severe COVID-19 condition.…”