Author Reply to: "Comment on 'The Prevalence of Olfactory and Gustatory Dysfunction in COVID-19 Patients: A Systematic Review and Meta-analysis'"

Chemical Constituents of Essential Oils Used in Olfactory Training: Focus on COVID-19 Induced Olfactory Dysfunction

The recent increase in the number of patients with post-viral olfactory dysfunction (PVOD) following the outbreak of COVID-19 has raised the general interest in and concern about olfactory dysfunction. At present, no clear method of treatment for PVOD has been established. Currently the most well-known method to improve the symptoms of olfactory dysfunction is "olfactory training" using essential oils. The essential oils used in olfactory training typically include rose, lemon, clove, and eucalyptus, which were selected based on the odor prism hypothesis proposed by Hans Henning in 1916. He classified odors based on six primary categories or dimensions and suggested that any olfactory stimulus fits into his smell prism, a three-dimensional space. The term "olfactory training" has been used based on the concept of training olfactory sensory neurons to relearn and distinguish olfactory stimuli. However, other mechanisms might contribute to how olfactory training can improve the recovery of the olfactory sense. Possibly, the essential oils contain chemical constituents with bioactive properties that facilitate the recovery of the olfactory sense by suppressing inflammation and enhancing regeneration. In this review, we summarize the chemical constituents of the essential oils of rose, lemon, clove, and eucalyptus and raise the possibility that the chemical constituents with bioactive properties are involved in improving the symptoms of olfactory dysfunction. We also propose that other essential oils that contain chemical constituents with anti-inflammatory effects and have binding affinity with SARS-CoV-2 can be new candidates to test their efficiencies in facilitating the recovery.

Progress in Traditional Chinese Medicine Against Respiratory Viruses: A Review

Respiratory viruses, such as severe acute respiratory syndrome coronavirus (SARS-CoV)-1, SARS-CoV-2, influenza A viruses, and respiratory syncytial virus, pose a serious threat to society. Based on the guiding principles of “holism” and “syndrome differentiation and treatment”, traditional Chinese medicine (TCM) has unique advantages in the treatment of respiratory virus diseases owing to the synergistic effect of multiple components and targets, which prevents drug resistance from arising. According to TCM theory, there are two main strategies in antiviral treatments, namely “dispelling evil” and “fu zheng”. Dispelling evil corresponds to the direct inhibition of virus growth and fu zheng corresponds to immune regulation, inflammation control, and tissue protection in the host. In this review, current progress in using TCMs against respiratory viruses is summarized according to modern biological theories. The prospects for developing TCMs against respiratory viruses is discussed to provide a reference for the research and development of innovative TCMs with multiple components, multiple targets, and low toxicity.

Neurological manifestations of COVID-19 infection: an umbrella review

BACKGROUND

Neurological involvements of COVID-19 are one of the most reported manifestations of this infection. This study aims to systematically review the previous systematic reviews which addressed the neurological manifestations of the COVID-19 infection.

METHODS

Following the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines, a comprehensive search was conducted in PubMed, Embase, Scopus, Web of Science databases and Google Scholar from December 2019 to December 2020. Articles were critically screened by two independent reviewers and if met the inclusion criteria, entered the study. Assessment of methodological quality was conducted by Assessment of Multiple Systematic Reviews-2 (AMSTAR-2) tool. Statistical analysis was not applicable. From a total of 1302 studies, 308 studies were removed due to their irrelevant title and abstract. After screening the full texts, a total of 66 found to be eligible. Twenty-one studies reported general manifestations of the COVID-19, 13 studies reported cerebrovascular events, 19 olfactory and oral dysfunctions, 5 systematic reviews on Guillen-Barré syndrome (GBS) and 8 articles on the sporadic manifestations like ocular signs and symptoms. The majority of the studies were classified as critically low or low in terms of quality.

CONCLUSION

Despite great heterogeneity in the current literature, neurological involvements are an important extra-pulmonary aspect of the COVID-19; most commonly in the form of general manifestations like headache and olfactory disturbances. Long-term effects of this virus on the nervous system must be a research priority for future references.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s41983-021-00366-5.

Diagnosis of Anosmia and Hyposmia: A Systematic Review

Background

Anosmia and hyposmia have many etiologies, including trauma, chronic sinusitis, neoplasms, and respiratory viral infections such as rhinovirus and SARS-CoV-2. We aimed to systematically review the literature on the diagnostic evaluation of anosmia/hyposmia.

Methods

PubMed, EMBASE, and Cochrane databases were searched for articles published since January 1990 using terms combined with Medical Subject Headings (MeSH). We included articles evaluating diagnostic modalities for anosmia, written in the English language, used original data, and had two or more patients.

Results

A total of 2065 unique titles were returned upon the initial search. Of these, 226 abstracts were examined, yielding 27 full-text articles meeting inclusion criteria (Level of evidence ranging from 1 to 4; most level 2). The studies included a total of 13,577 patients. The most utilized diagnostic tools were orthonasal smell tests (such as the Sniffin’ Sticks and the UPSIT, along with validated abridged smell tests). Though various imaging modalities (including MRI and CT) were frequently mentioned in the workup of olfactory dysfunction, routine imaging was not used to primarily diagnose smell loss.

Conclusion

The literature includes several studies on validity and reliability for various smell tests in diagnosing anosmia. Along with a thorough history and physical, validated orthonasal smell tests should be part of the workup of the patient with suspected olfactory dysfunction. The most widely studied modality was MRI, but criteria for the timing and sequence of imaging modalities was heterogenous.

COVID-19 experience of the major pandemic response center in the capital: results of the pandemic’s first month in Turkey

Background/aim

The aim of this study is to evaluate the epidemiological and clinical characteristics and parameters that determined the clinical course and prognosis of the COVID-19 patients admitted to Ankara City Hospital during the first month of the pandemic in Turkey.

Materials and methods

SARS-CoV-2 PCR positive patients who were hospitalized between March 10 and April 10, 2020 were included.

Results

Among 222 patients, mean age was higher in severe acute respiratory illness (SARI)/critical disease group (P < 0.001). Median time from illness onset to admission and presence of comorbidity, especially coronary artery disease and chronic obstructive pulmonary disease, were significantly higher in the SARI/critical disease group (P < 0.05). Cough and fever were the most common symptoms, while anosmia and loss of taste were observed in 8.6% and 7.7% patients, respectively. The mortality rate was 5.4%. A high neutrophil/lymphocyte ratio; low lymphocyte, monocyte, and platelet count; elevated liver enzymes; low GFR; and high levels of muscle enzymes, ferritin, and IL-6 on admission were found to be associated with SARI/critical disease (P < 0.05). Bilateral ground-glass opacity and patchy infiltration were more frequently seen in the SARI/critical disease group (P < 0.001). Patients older than 65 years had an 8-fold increased risk for development of SARI/critical disease.

Conclusion

This cohort study regarding COVID-19 cases in Turkey reveals that older age, presence of comorbidity, bilateral infiltration on CT, high neutrophil/lymphocyte ratio, low monocyte and platelet count, elevated liver enzymes, low GFR, high levels of muscle enzymes, and high levels of ferritin and IL-6 on admission are predictors of SARI and severe disease.

Symptoms and symptom clusters associated with SARS-CoV-2 infection in community-based populations: Results from a statewide epidemiological study

Background:

Prior studies examining symptoms of COVID-19 are primarily descriptive and measured among hospitalized individuals. Understanding symptoms of SARS-CoV-2 infection in pre-clinical, community-based populations may improve clinical screening, particularly during flu season. We sought to identify key symptoms and symptom combinations in a community-based population using robust methods.

Methods:

We pooled community-based cohorts of individuals aged 12 and older screened for SARS-CoV-2 infection in April and June 2020 for a statewide seroprevalence study. Main outcome was SARS-CoV-2 positivity. We calculated sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for individual symptoms as well as symptom combinations. We further employed multivariable logistic regression and exploratory factor analysis (EFA) to examine symptoms and combinations associated with SARS-CoV-2 infection.

Results:

Among 8214 individuals screened, 368 individuals (4.5%) were RT-PCR positive for SARS-CoV-2. Although two-thirds of symptoms were highly specific (>90.0%), most symptoms individually possessed a PPV <50.0%. The individual symptoms most greatly associated with SARS-CoV-2 positivity were fever (OR=5.34, p<0.001), anosmia (OR=4.08, p<0.001), ageusia (OR=2.38, p=0.006), and cough (OR=2.86, p<0.001). Results from EFA identified two primary symptom clusters most associated with SARS-CoV-2 infection: (1) ageusia, anosmia, and fever; and (2) shortness of breath, cough, and chest pain. Moreover, being non-white (13.6% vs. 2.3%, p<0.001), Hispanic (27.9% vs. 2.5%, p<0.001), or living in an Urban area (5.4% vs. 3.8%, p<0.001) was associated with infection.

Conclusions:

Symptoms can help distinguish SARS-CoV-2 infection from other respiratory viruses, especially in community or urgent care settings where rapid testing may be limited. Symptoms should further be structured in clinical documentation to support identification of new cases and mitigation of disease spread by public health. These symptoms, derived from asymptomatic as well as mildly infected individuals, can also inform vaccine and therapeutic clinical trials.

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

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.

Taste and Smell Impairment in COVID-19: An AAO-HNS Anosmia Reporting Tool-Based Comparative Study

OBJECTIVE

To identify the taste and smell impairment in coronavirus disease 2019 (COVID-19)-positive subjects and compare the findings with COVID-19-negative subjects using the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) Anosmia Reporting Tool.

SETTING

Tertiary referral center/COVID-19 pandemic hospital.

STUDY DESIGN

Comparative study.

SUBJECTS AND METHODS

After power analysis, 128 subjects were divided into 2 groups according to real-time polymerase chain reaction (RT-PCR) COVID-19 testing results. Subjects were called via telephone, and the AAO-HNS Anosmia Reporting Tool was used to collect responses.

RESULTS

The mean age of the study group was 38.63 ± 10.08 years. At the time of sampling, rhinorrhea was significantly high in the COVID-19-negative group, whereas those complaints described as "other" were significantly high in the COVID-19-positive group. There was a significant difference in the smell/taste impairment rates of the groups (n = 46% [71.9%] for the COVID-19-positive group vs n = 17 [26.6%] for the COVID-19-negative group, P = .001). For subjects with a smell impairment, anosmia rates did not differ between the groups. The rates of hyposmia and parosmia were significantly high in the COVID-19-positive group. For the subjects with taste impairment, ageusia rates did not differ between groups. The rate of hypogeusia and dysgeusia was significantly high in the COVID-19-positive group. Logistic regression analysis indicates that smell/taste impairment in COVID-19-positive subjects increases the odds ratio by 6.956 (95% CI, 3.16-15.29) times.

CONCLUSION

COVID-19-positive subjects are strongly associated with smell/taste impairment.

Smell and Taste Dysfunction in Patients With COVID-19: A Systematic Review and Meta-analysis

OBJECTIVE

To estimate the prevalence of olfactory and gustatory dysfunctions (OGDs) among patients infected with novel coronavirus disease 2019 (COVID-19).

METHODS

A systematic review was conducted by searching MEDLINE, EMBASE, and the preprint server MedRxiv from their inception until May 11, 2020, using the terms anosmia or hyposmia or dysosmia or olfactory dysfunction or olfaction disorder or smell dysfunction or ageusia or hypogeusia or dysgeusia or taste dysfunction or gustatory dysfunction or neurological and COVID-19 or 2019 novel coronavirus or 2019-nCoV or SARS-CoV-2. The references of included studies were also manually screened. Only studies involving patients with diagnostic-confirmed COVID-19 infection were included. Random-effects meta-analysis was performed.

RESULTS

Twenty-four studies with data from 8438 patients with test-confirmed COVID-19 infection from 13 countries were included. The pooled proportions of patients presenting with olfactory dysfunction and gustatory dysfunction were 41.0% (95% CI, 28.5% to 53.9%) and 38.2% (95% CI, 24.0% to 53.6%), respectively. Increasing mean age correlated with lower prevalence of olfactory (coefficient = -0.076; P=.02) and gustatory (coefficient = -0.073; P=.03) dysfunctions. There was a higher prevalence of olfactory dysfunctions with the use of objective measurements compared with self-reports (coefficient = 2.33; P=.01). No significant moderation of the prevalence of OGDs by sex was observed.

CONCLUSION

There is a high prevalence of OGDs among patients infected with COVID-19. Routine screening for these conditions could contribute to improved case detection in the ongoing COVID-19 pandemic. However, to better inform population screening measures, further studies are needed to establish causality.

Ageusia and anosmia, a common sign of COVID-19? A case series from four countries

Over the course of the pandemic due to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), multiple new clinical manifestations, as the consequence of the tropism of the virus, have been recognized. That includes now the neurological manifestations and conditions, such as headache, encephalitis, as well as olfactory and taste disorders. We present a series of ten cases of RT-PCR-confirmed SARS-CoV-2-infected patients diagnosed with viral-associated olfactory and taste loss from four different countries.

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

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.