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

Cognitive deficits and cortical volume loss in COVID-19-related hyposmia

BACKGROUND AND PURPOSE

Studies have found that up to 73% of COVID-19 patients experience hyposmia. It is unclear if the loss of smell in COVID-19 is due to damage to the peripheral or central mechanisms. This study aimed to explore the impacts of COVID-19-induced hyposmia on brain structure and cognitive functions.

METHODS

The study included 36 hyposmic (h-COV) and 21 normosmic (n-COV) participants who had recovered from mild COVID-19 infection, as well as 25 healthy controls (HCs). All participants underwent neurological examination, neuropsychiatric assessment and Sniffin' Sticks tests. High-resolution anatomical images were collected; olfactory bulb (OB) volume and cortical thickness were measured.

RESULTS

Addenbrooke's Cognitive Examination-Revised total and language sub-scores were slightly but significantly lower in the h-COV group compared to the HC group (p = 0.04 and p = 0.037). The h-COV group exhibited poorer performance in the Sniffin' Sticks test terms of discrimination score, identification score and the composite score compared to the n-COV and HC groups (p < 0.001, p = 0.001 and p = 0.002 respectively). A decrease in left and right OB volumes was observed in the h-COV group compared to the n-COV and HC groups (p = 0.003 and p = 0.006 respectively). The cortical thickness analysis revealed atrophy in the left lateral orbitofrontal cortex in the h-COV group compared to HCs. A significant low positive correlation of varying degrees was detected between discrimination and identification scores and both OB and left orbital sulci.

CONCLUSION

Temporary or permanent hyposmia after COVID-19 infection leads to atrophy in the OB and olfactory-related cortical structures and subtle cognitive problems in the long term.

Neuropathological assessment of the olfactory bulb and tract in individuals with COVID-19

The majority of patients with Parkinson disease (PD) experience a loss in their sense of smell and accumulate insoluble α-synuclein aggregates in their olfactory bulbs (OB). Subjects affected by a SARS-CoV-2-linked illness (COVID-19) also frequently experience hyposmia. We previously postulated that microglial activation as well as α-synuclein and tau misprocessing can occur during host responses following microbial encounters. Using semiquantitative measurements of immunohistochemical signals, we examined OB and olfactory tract specimens collected serially at autopsies between 2020 and 2023. Deceased subjects comprised 50 adults, which included COVID19 + patients (n = 22), individuals with Lewy body disease (e.g., PD; dementia with Lewy bodies (n = 6)), Alzheimer disease (AD; n = 3), and other neurodegenerative disorders (e.g., progressive supranuclear palsy (n = 2); multisystem atrophy (n = 1)). Further, we included neurologically healthy controls (n = 9), and added subjects with an inflammation-rich brain disorder as neurological controls (NCO; n = 7). When probing for microglial and histiocytic reactivity in the anterior olfactory nuclei (AON) by anti-CD68 immunostaining, scores were consistently elevated in NCO and AD cases. In contrast, microglial signals on average were not significantly altered in COVID19 + patients relative to healthy controls, although anti-CD68 reactivity in their OB and tracts declined with progression in age. Mild-to-moderate increases in phospho-α-synuclein and phospho-tau signals were detected in the AON of tauopathy- and synucleinopathy-afflicted brains, respectively, consistent with mixed pathology, as described by others. Lastly, when both sides were available for comparison in our case series, we saw no asymmetry in the degree of pathology of the left versus right OB and tracts. We concluded from our autopsy series that after a fatal course of COVID-19, microscopic changes in the rostral, intracranial portion of the olfactory circuitry -when present- reflected neurodegenerative processes seen elsewhere in the brain. In general, microglial reactivity correlated best with the degree of Alzheimer's-linked tauopathy and declined with progression of age in COVID19 + patients.

Validation of a questionnaire assessing smell loss in an international aspirin-exacerbated respiratory disease population

Background: Olfactory dysfunction (OD) and smell loss affects aspects of patients' everyday life and lowers their quality of life. OD questionnaires are considered one of the core-outcome measures in chronic rhinosinusitis, but many existing smell loss questionnaires contained pandemic-prohibitive questions on social gatherings or restaurant visits, were too culture specific or gender specific, or were overly long and cumbersome. Objective: We aimed to develop a new brief questionnaire to assess the impact and consequences of smell loss and its burden on daily life. This study validates this new, short, multicultural, dichotomized questionnaire in an international population that has aspirin-exacerbated disease (AERD). Methods: The Consequences of Smell Loss (COSL) questionnaire was developed and content validity was assessed by experts and patients at Brigham and Women's Hospital. The questionnaire, along with other validated quality-of-life surveys, was answered by 853 patients with AERD. We evaluated the factor structure, reliability, validity, and discriminative ability of the COSL questionnaire. Results: The final version of the COSL questionnaire consisted of 13 items divided into three subdomains (emotional distress, food and safety, and physical health) through factor analysis. The Cronbach α for internal consistency was 0.82. Convergent and discriminant validity with the 22-item Sinonasal Outcome Test (SNOT-22), Healthy Days Core Module-4, Patient Health Questionnaire-4, and a specific question on taste and smell were high (p < 0.0001 for all). The COSL questionnaire score was associated with SNOT-22 categories (p < 0.001) and was categorized as follows: normal, 0-1 points; very few consequences, 2-3 points; few, 4 points; moderate, 5-6 points; and severe, 7-13 points. Conclusion: The COSL questionnaire is a new, brief, valid, reliable tool that can effectively screen for a high burden of OD in patients with AERD and has the potential to be used in other patient populations with OD as well.

Epidemiological, clinical and laboratory profile of patients presenting with severe acute respiratory syndrome (SARS-CoV-2) in Ethiopia

INTRODUCTION

Data regarding patients presenting with severe acute respiratory syndrome (SARS-CoV-2) illness have not adequately been documented which provides distinct insights into low-resource settings like Ethiopia. Thus, the study aimed to compare epidemiological, clinical and laboratory profiles of patients presenting with acute respiratory syndrome illness in Addis Ababa Ethiopia.

METHODS

We used a comparative cross-sectional study design among patients with SARS-CoV-2 illness at St. Paul's Hospital Millennium Medical College (SPHMMC), Addis Ababa, Ethiopia from October 2020 to September 2021. Using a structured questionnaire a consecutive sampling technique was applied to collect socio-demographic data. Additionally, nasal swabs were collected to confirm SARS-CoV-2 infection using a Real-Time Polymerase Chain Reaction. Blood samples were also collected from the participants for laboratory profiles (hematological tests like; white blood cell count, hematocrit, and platelet count; and biochemical and enzymatic tests like; aspartate transaminase (AST), creatinine, etc) analysis. Data were entered and analyzed using SPSS version 23.0 and p-values ≤0.05 were considered as statistically significant.

RESULTS

Of the total 413 participants presenting with SARS-CoV-2 illness, 250 (60.5%) participants tested positive for COVID-19 disease. COVID-19 patients were less likely to use an alcohol-based method of hand washing (12.5% vs 87.5%; p = 0.048). The COVID-19 patients had a higher proportion of headache (67.3% vs 32.7%, p = 0.001), sore throat (72.5% vs 27.5%, p = 0.001), and loss of sense of taste (74.4% vs 25.6%, p = 0.002). Patients with COVID-19 have significantly higher neutrophil than their counterparts (68.2% vs 31.8%; p = 0.001). Similarly, creatinine (64.9% vs 35.1%, p = 0.001) from renal function and alkaline phosphatase (66.8% vs 33.2%, p = 0.046) in the liver function tests were significantly higher in the COVID-19 patients.

CONCLUSION

Our findings suggest the need to substantially consider headache, sore throat, and loss of taste as potential clinical diagnostic symptoms for early screening and testing. Elevation of neutrophil, creatinine, alkaline phosphatase profiles are also used for potential diagnostic biomarkers in screening and testing suspected patients.

Olfactory dysfunction among patients with COVID-19

OBJECTIVES

To assess the frequency of olfactory dysfunction (OD) among individuals afflicted with coronavirus disease of 2019 (COVID-19).

METHODS

A comprehensive literature search was carried out across several bibliographical databases (PubMed, Scopus, Google Scholar, and Web of Science) to extract publications in the English language between January 2020 and December 2021 to report the incidence of OD alone or together with gustatory dysfunction (GD) among COVID-19 patients.

RESULTS

Based on eligibility criteria, 84 articles were included from 27 countries, comprising 36,903 patients, of whom 58.1% were females. The generality rates of olfactory impairment alone was 34.60% and in conjunction with GD was 11.36%. Patients with OD were subclassified into various categories, and the prevalence of anosmia was 20.85%, 5.04% for hyposmia, 8.88% for anosmia or hyposmia, 1.84% for parosmia, 0.78% for phantosmia, and 0.02% for hyperosmia, among COVID-19 patients.

CONCLUSION

Clinical features associated with OD, either isolated or in combination with GD, are common in patients with COVID-19 and consider important signs of COVID-19 that may guide clinicians in the early phase of the disease.PROSPERO Reg. No.: 417296.

Hyposmia in COVID-19: Temporal Recovery of Smell: A Preliminary Study

Background and Objectives: Hypo/anosmia is a characteristic symptom of COVID-19 infection. The aim of this study is to investigate the time of smell recovery and to identify a possible order of perception recovery of different odors in COVID-19 patients. Materials and Methods: A prospective observational study was conducted on not hospitalized COVID-19 patients, selected according to eligible criteria. The study was approved by the Ethical Committee. A questionnaire formulated by our team was submitted to patients in order to know the duration of the hypo/anosmia and hypo/ageusia and the order of odor recovery: vanillin (mixed olfactory/gustatory substances), phenyl ethyl alcohol (rosewater) (pure olfactory substances), eucalyptol (mixed olfactory/trigeminal substances), and eugenol (mixed olfactory/trigeminal/gustatory substances). Results: 181 patients were included. Hypo/ageusia and hypo/anosmia lasted on average 10.25 (±8.26) and 12.8 (±8.80) days, respectively. The most frequent odor recovery sequence was: (1) phenyl ethyl alcohol; (2) eucalyptol; (3) vanillin; and (4) eugenol. In COVID-19 patients, hypo/anosmia occurs more often in women and at a young age. Conclusions: This preliminary investigation highlighted novel data: there is a chronological order in perception recovery of different olfactory substances and, therefore, in the restoration of the various sensitive nerve pathways involved in the sense of smell.

Altered structural connectivity in olfactory disfunction after mild COVID-19 using probabilistic tractography

We aimed to investigate changes in olfactory bulb volume and brain network in the white matter (WM) in patients with persistent olfactory disfunction (OD) following COVID-19. A cross-sectional study evaluated 38 participants with OD after mild COVID-19 and 24 controls, including Sniffin' Sticks identification test (SS-16), MoCA, and brain magnetic resonance imaging. Network-Based Statistics (NBS) and graph theoretical analysis were used to explore the WM. The COVID-19 group had reduced olfactory bulb volume compared to controls. In NBS, COVID-19 patients showed increased structural connectivity in a subnetwork comprising parietal brain regions. Regarding global network topological properties, patients exhibited lower global and local efficiency and higher assortativity than controls. Concerning local network topological properties, patients had reduced local efficiency (left lateral orbital gyrus and pallidum), increased clustering (left lateral orbital gyrus), increased nodal strength (right anterior orbital gyrus), and reduced nodal strength (left amygdala). SS-16 test score was negatively correlated with clustering of whole-brain WM in the COVID-19 group. Thus, patients with OD after COVID-19 had relevant WM network dysfunction with increased connectivity in the parietal sensory cortex. Reduced integration and increased segregation are observed within olfactory-related brain areas might be due to compensatory plasticity mechanisms devoted to recovering olfactory function.

Omega-3 Fatty Acid Supplementation for the Treatment of Persistent COVID-Related Olfactory Dysfunction

OBJECTIVE

To evaluate the efficacy of omega-3 fatty acid (O3FA) supplementation in the treatment of COVID-related olfactory dysfunction (OD).

METHODS

Patients with laboratory-confirmed or clinically-suspected COVID-19 infection and new-onset OD from August 2020 to November 2021 were prospectively recruited. Patients with quantitative OD, defined as a brief smell identification test (BSIT) score of 9 or less, were eligible for study inclusion. The experimental group received 2 g of O3FA supplementation, while the control group received an identical placebo to be taken daily for 6 weeks. The primary outcome was a change in BSIT score between the initial and 6-week follow-up tests.

RESULTS

One hundred and seventeen patients were included in the analysis, including 57 patients in the O3FA group and 60 in the placebo group. O3FA group patients demonstrated a mean BSIT improvement of 1.12 ± 1.99 compared to 0.68 ± 1.86 in the placebo group (p = 0.221). Seventy-seven patients, 42 within the O3FA group and 35 in the placebo group, completed a follow-up BSIT survey at an average of 717.8 days from study onset. At long-term follow-up, there was an average BSIT score improvement of 1.72 within the O3FA group compared to 1.76 within the placebo group (p = 0.948).

CONCLUSION

Among patients with persistent COVID-related OD, our study showed no clear evidence of relative short-term or long-term olfactory recovery among patients receiving high doses of O3FA supplementation.

[Interpretation of the 2021 American Academy of Allergy, Asthma and Immunology expert consensus on the treatment of postinfectious olfactory dysfunction]

Respiratory tract viruses are the second leading cause of olfactory dysfunction. Between 2019 to 2022, the world has been plagued by the problem of olfaction caused by the COVID-19. As we learn more about the impact of severe acute respiratory syndrome coronavirus 2（SARS-CoV-2）, with the recognition that olfactory dysfunction is a key symptom of this disease process, there is a greater need than ever for evidence-based management of postinfectious olfactory dysfunction（PIOD）. The Clinical Olfactory Working Group has proposed theconsensus on the roles of PIOD. This paper is the detailed interpretation of the consensus.

Qualitative Olfactory Dysfunction and COVID-19: An Evidence-Based Review with Recommendations for the Clinician

BACKGROUND

Nearly 40% of patients who experience smell loss during SARS-CoV-2 infection may develop qualitative olfactory dysfunction, most commonly parosmia. Our evidence-based review summarizes the evolving literature and offers recommendations for the clinician on the management of patients experiencing parosmia associated with COVID-19.

METHODS

We performed a systematic search using independent queries in PubMed, Embase, Ovid, and Cochrane databases, then categorized articles according to themes that emerged regarding epidemiology, effect on quality of life, disease progression, prognosis, pathophysiology, diagnosis, and treatment of parosmia.

RESULTS

We identified 123 unique references meeting eligibility and performed title and abstract review with 2 independent reviewers, with 74 articles undergoing full-text review. An inductive approach to thematic development provided 7 central themes regarding qualitative olfactory dysfunction following COVID-19.

CONCLUSIONS

While other respiratory viruses are known to cause qualitative olfactory disturbances, the incidence of parosmia following COVID-19 is notable, and correlates negatively with age. The presence of parosmia predicts persistent quantitative olfactory dysfunction. Onset can occur months after infection, and symptoms may persist for well over 7 months. Affected patients report increased anxiety and decreased quality of life. Structured olfactory training with essential oils is the preferred treatment, where parosmia predicts recovery of aspects of quantitative smell loss when undergoing training. There is limited evidence that nasal corticosteroids may accelerate recovery of olfactory function. Patients should be prepared for the possibility that symptoms may persist for years, and providers should guide them to resources for coping with their psychosocial burden.

Taste loss as a distinct symptom of COVID-19: a systematic review and meta-analysis

Chemosensory scientists have been skeptical that reports of COVID-19 taste loss are genuine, in part because before COVID-19 taste loss was rare and often confused with smell loss. Therefore, to establish the predicted prevalence rate of taste loss in COVID-19 patients, we conducted a systematic review and meta-analysis of 376 papers published in 2020-2021, with 235 meeting all inclusion criteria. Drawing on previous studies and guided by early meta-analyses, we explored how methodological differences (direct vs. self-report measures) may affect these estimates. We hypothesized that direct measures of taste are at least as sensitive as those obtained by self-report and that the preponderance of evidence confirms taste loss is a symptom of COVID-19. The meta-analysis showed that, among 138,015 COVID-19-positive patients, 36.62% reported taste dysfunction (95% confidence interval: 33.02%-40.39%), and the prevalence estimates were slightly but not significantly higher from studies using direct (n = 15) versus self-report (n = 220) methodologies (Q = 1.73, df = 1, P = 0.1889). Generally, males reported lower rates of taste loss than did females, and taste loss was highest among middle-aged adults. Thus, taste loss is likely a bona fide symptom of COVID-19, meriting further research into the most appropriate direct methods to measure it and its underlying mechanisms.

Prevalence, Patterns, Prognosis, and Psychosocial Impact of Olfactory and Gustative Dysfunctions Among Saudi COVID-19 Patients

Objective The objective of this study is to estimate the prevalence of olfactory and gustative dysfunctions (OGD) and analyze their pattern and psychosocial impact among COVID-19 patients. Method A cross-sectional study was conducted among 194 confirmed COVID-19 cases at Al-Noor Specialist Hospital between 1 September 2020 and 30 September 2021. A questionnaire was translated and modified from another study to collect the baseline demographic data and medical history; characterization of smell and taste loss separately, including timing, level, practices or treatment used to restore, recovery, and symptom duration; and the psychological impact of OGD using six items to explore the multidimensional impact, such as daily activity, job performance, and social life. A four-point Likert-type agreement scale was used, and an impact score was calculated. Result As high as 97.4% and 94.8% of the participants declared having experienced a certain level of olfactory and gustative dysfunction, respectively. In the majority of these cases, the dysfunction occurred after the acute phase of the disease and persisted less than one month after onset. Social life (78.4%), job performance (64.4%), and daily life activities (42.8%) were the most frequently impacted dimensions, and 32% of the participants were deemed to have experienced a high psychosocial impact. Younger participants, females, and certain job categories were significantly more impacted than their counterparts. Conclusion OGDs are highly frequent in COVID-19 patients. They are described to be relatively severe and have frequent psychosocial impacts, notably in females and the younger age category. Further research is warranted to determine efficacious preventive and management strategies in order to prevent their long-term impact on wellbeing.

Olfactory distortions in the general population

Parosmia, distorted smell sensations, is a common consequence of respiratory virus infections. The phenomenon is not well understood in terms of its impact and long-term outcomes. We examined self-reported experiences of parosmia in a population-based sample from the Betula study that was conducted in Umeå in northern Sweden (baseline data collected in 1998–2000). We used a baseline sample of 2168 individuals aged 35–90 years and with no cognitive impairment at baseline. We investigated the prevalence of parosmia experiences and, using regression analyses, its relationship to other olfactory and cognitive variables and quality of life. Benefitting from the longitudinal study design, we also assessed the persistence of parosmia over 5 and 10 years prospectively. Parosmia experiences were prevalent in 4.8% of the population and it often co-occurred with phantosmia (“olfactory hallucinations”), but was not associated with lower self-rated overall quality of life or poor performance on olfactory or cognitive tests. For some individuals, parosmia was retained 5 years (17.0%) or even 10 years later (10.3%). Thus, parosmia experiences are commonly reported in the population, and can be persistent for some individuals, but might be mostly benign in nature. Our work complements research on clinical-level parosmia, which is typically more severe, and recent parosmia reports during the COVID-19 pandemic, where long-term outcomes are still unknown.

Postmortem Assessment of Olfactory Tissue Degeneration and Microvasculopathy in Patients With COVID-19

Importance

Loss of smell is an early and common presentation of COVID-19 infection. Although it has been speculated that viral infection of olfactory neurons may be the culprit, it is unclear whether viral infection causes injuries in the olfactory bulb region.

Objective

To characterize the olfactory pathology associated with COVID-19 infection in a postmortem study.

Design, Setting, and Participants

This multicenter postmortem cohort study was conducted from April 7, 2020, to September 11, 2021. Deceased patients with COVID-19 and control individuals were included in the cohort. One infant with congenital anomalies was excluded. Olfactory bulb and tract tissue was collected from deceased patients with COVID-19 and appropriate controls. Histopathology, electron microscopy, droplet digital polymerase chain reaction, and immunofluorescence/immunohistochemistry studies were performed. Data analysis was conducted from February 7 to October 19, 2021.

Main Outcomes and Measures

(1) Severity of degeneration, (2) losses of olfactory axons, and (3) severity of microvasculopathy in olfactory tissue.

Results

Olfactory tissue from 23 deceased patients with COVID-19 (median [IQR] age, 62 [49-69] years; 14 men [60.9%]) and 14 control individuals (median [IQR] age, 53.5 [33.25-65] years; 7 men [50%]) was included in the analysis. The mean (SD) axon pathology score (range, 1-3) was 1.921 (0.569) in patients with COVID-19 and 1.198 (0.208) in controls (P < .001), whereas axon density was 2.973 (0.963) × 104/mm2 in patients with COVID-19 and 3.867 (0.670) × 104/mm2 in controls (P = .002). Concomitant endothelial injury of the microvasculature was also noted in olfactory tissue. The mean (SD) microvasculopathy score (range, 1-3) was 1.907 (0.490) in patients with COVID-19 and 1.405 (0.233) in control individuals (P < .001). Both the axon and microvascular pathology was worse in patients with COVID-19 with smell alterations than those with intact smell (mean [SD] axon pathology score, 2.260 [0.457] vs 1.63 [0.426]; P = .002; mean [SD] microvasculopathy score, 2.154 [0.528] vs 1.694 [0.329]; P = .02) but was not associated with clinical severity, timing of infection, or presence of virus.

Conclusions and Relevance

This study found that COVID-19 infection is associated with axon injuries and microvasculopathy in olfactory tissue. The striking axonal pathology in some cases indicates that olfactory dysfunction in COVID-19 infection may be severe and permanent.

Association between chemosensory impairment with neuropsychiatric morbidity in post-acute COVID-19 syndrome: results from a multidisciplinary cohort study

Preliminary methodologically limited studies suggested that taste and smell known as chemosensory impairments and neuropsychiatric symptoms are associated in post-COVID-19. The objective of this study is to evaluate whether chemosensory dysfunction and neuropsychiatric impairments in a well-characterized post-COVID-19 sample. This is a cohort study assessing adult patients hospitalized due to moderate or severe forms of COVID-19 between March and August 2020. Baseline information includes several clinical and hospitalization data. Further evaluations were made using several different reliable instruments designed to assess taste and smell functions, parosmia, and neuropsychiatric disorders (using standardized psychiatric and cognitive measures). Out of 1800 eligible individuals, 701 volunteers were assessed on this study. After multivariate analysis, patients reporting parosmia had a worse perception of memory performance (p < 0.001). Moderate/severe hypogeusia was significantly associated with a worse performance on the word list memory task (p = 0.012); Concomitant moderate/severe olfactory and gustatory loss during the acute phase of COVID-19 was also significantly associated with episodic memory impairment (p = 0.006). We found a positive association between reported chemosensory (taste and olfaction) abnormalities and cognition dysfunction in post-COVID-19 patients. These findings may help us identify potential mechanisms linking these two neurobiological functions, and also support the speculation on a possible route through which SARS-CoV-2 may reach the central nervous system.

Five-item odorant test as an indicator of COVID-19 infection in a general population

Purpose

To analyze the utility of a 5-item odorant test (U-Smell-It™) in determining COVID-19 status in COVID-19 polymerase chain reaction (PCR)-positive and -negative participants.

Methods

Symptoms, COVID-19 status, and 5-item odorant test results were collected from general population COVID-19 testing in Louisiana (n = 1042), and routine COVID-19 screening of healthcare workers in a nursing home in Florida (n = 278) (ClinicalTrials.gov Identifier: NCT04431908).

Results

In the general population COVID-19 testing site, a cutoff point of ≤2 (0, 1, or 2 correct answers out of 5) achieved sensitivity of 40.0% (95% CI: 26.4%–54.8%) and specificity of 89.2% (95% CI: 87.1%–91.1%) in detecting COVID-19 infection. Within this population, analysis of individuals with no self-reported loss of smell/taste and runny/stuffy nose resulted in sensitivity of 38.1% (95% CI: 18.1%–61.6%) and specificity of 92.3% (95% CI: 89.1%–93.4%), while analysis of individuals with self-reported loss of smell/taste and/or runny/stuffy nose resulted in sensitivity of 41.4% (95% CI: 23.5%–61.1%) and specificity of 82.4% (95% CI: 77.7%–86.5%).

Conclusions

The quick turnaround time, low cost, reduced resource requirement, and ease of administering odorant tests provide many advantages as an indicator sign to help flag a molecular diagnostic COVID-19 test with relatively high specificity. Our results suggest that this odorant testing for olfactory dysfunction may be a viable option in pre-screening COVID-19 infection. This tool has the potential to allow for continued monitoring and surveillance, while helping mitigate surges of COVID-19 variants. Further investigation is warranted to observe the extent to which odorant testing might be applied in a serial testing scenario.

Olfactory Dysfunction in Patients With Coronavirus Disease 2019: A Review

The coronavirus disease 2019 (COVID-19) pandemic is wreaking havoc on public-health and economic systems worldwide. Among the several neurological symptoms of patients with COVID-19 reported in clinical practice, olfactory dysfunction (OD) is the most common. OD occurs as the earliest or the only clinical manifestation in some patients. Increasing research attention has focused on OD, which is listed as one of the main diagnostic symptoms of severe acute respiratory syndrome-coronavirus-2 infection. Multiple clinical and basic-science studies on COVID-19-induced OD are underway to clarify the underlying mechanism of action. In this review, we summarize the clinical characteristics, mechanisms, evaluation methods, prognosis, and treatment options of COVID-19-induced OD. In this way, we hope to improve the understanding of COVID-19-induced OD to aid early identification and precise intervention.

Taste loss as a distinct symptom of COVID-19: a systematic review and meta-analysis

Chemosensory scientists have been skeptical that reports of COVID-19 taste loss are genuine, in part because before COVID-19 taste loss was rare and often confused with smell loss. Therefore, to establish the predicted prevalence rate of taste loss in COVID-19 patients, we conducted a systematic review and meta-analysis of 376 papers published in 2020-2021, with 241 meeting all inclusion criteria. Drawing on previous studies and guided by early meta-analyses, we explored how methodological differences (direct vs. self-report measures) may affect these estimates. We hypothesized that direct measures of taste are at least as sensitive as those obtained by self-report and that the preponderance of evidence confirms taste loss is a symptom of COVID-19. The meta-analysis showed that, among 138,897 COVID-19-positive patients, 39.2% reported taste dysfunction (95% confidence interval: 35.34%-43.12%), and the prevalence estimates were slightly but not significantly higher from studies using direct (n = 18) versus self-report (n = 223) methodologies (Q = 0.57, df = 1, P = 0.45). Generally, males reported lower rates of taste loss than did females, and taste loss was highest among middle-aged adults. Thus, taste loss is likely a bona fide symptom of COVID-19, meriting further research into the most appropriate direct methods to measure it and its underlying mechanisms.

Exploring the Clinical Utility of Gustatory Dysfunction (GD) as a Triage Symptom Prior to Reverse Transcription Polymerase Chain Reaction (RT-PCR) in the Diagnosis of COVID-19: A Meta-Analysis and Systematic Review

BACKGROUND

The diagnosis of COVID-19 is made using reverse transcription polymerase chain reaction (RT-PCR) but its sensitivity varies from 20 to 100%. The presence of gustatory dysfunction (GD) in a patient with upper respiratory tract symptoms might increase the clinical suspicion of COVID-19.

AIMS

To perform a systematic review and meta-analysis to determine the pooled sensitivity, specificity, positive likelihood ratio (LR+), negative likelihood ratio (LR-) and diagnostic odds ratio (DOR) of using GD as a triage symptom prior to RT-PCR.

METHODS

PubMed and Embase were searched up to 20 June 2021. Studies published in English were included if they compared the frequency of GD in COVID-19 adult patients (proven by RT-PCR) to COVID-19 negative controls in case control or cross-sectional studies. The Newcastle-Ottawa scale was used to assess the methodological quality of the included studies.

RESULTS

21,272 COVID-19 patients and 52,298 COVID-19 negative patients were included across 44 studies from 21 countries. All studies were of moderate to high risk of bias. Patients with GD were more likely to test positive for COVID-19: DOR 6.39 (4.86-8.40), LR+ 3.84 (3.04-4.84), LR- 0.67 (0.64-0.70), pooled sensitivity 0.37 (0.29-0.47) and pooled specificity 0.92 (0.89-0.94). While history/questionnaire-based assessments were predictive of RT-PCR positivity (DOR 6.62 (4.95-8.85)), gustatory testing was not (DOR 3.53 (0.98-12.7)). There was significant heterogeneity among the 44 studies (I2 = 92%, p < 0.01).

CONCLUSIONS

GD is useful as a symptom to determine if a patient should undergo further testing, especially in resource-poor regions where COVID-19 testing is scarce. Patients with GD may be advised to quarantine while repeated testing is performed if the initial RT-PCR is negative.

FUNDING

None.

Central nervous system as a target of novel coronavirus infections: Potential routes of entry and pathogenic mechanisms

Since the COVID-19 pandemic started in December 2019, there have been several reports of patients succumbing to neurological complications. Early reports were suggestive of a possibility, while by early 2020 it was clearly evident that although SARS-CoV-2 primarily attacks the respiratory system, the brain is one of the most affected organs post-recovery. Although it may be premature to comment on the long-term effects of COVID-19 in brain, some reliable predictions can be made based on the data currently available. Further, exploring the CNS connections of SARS-CoV-2 is of keen interest for neuroscience researchers. As soon as the virus enters the nasal region, it is exposed to the olfactory nervous system which is interlinked with the visual system, and hence we explore the mechanism of entry of this virus into CNS, including brain, olfactory and retinal nervous systems. In this review, we have thoroughly reviewed reports about both SARS-CoV-1 and SARS-CoV-2 with respect to their ability to breach the blood-brain and blood-retinal barriers. We have compiled different neurological conditions resulting from COVID-19 and looked into viral infections related to COVID-19 to understand how the virus may gain control of the olfactory and visual systems. Once the dust settles on the pandemic, it would be interesting to explore the extent of viral infection in the CNS. The long-term effects of this virus in the CNS are not yet known, and several scientific research papers evolving in this field will throw light on the same.

Dysgeusia: A review in the context of COVID-19

Background

Taste disorders in general, and dysgeusia in particular, are relatively common disorders that may be a sign of a more complex acute or chronic medical condition. During the COVID-19 pandemic, taste disorders have found their way into the realm of general as well as specialty dentistry, with significance in screening for patients who potentially may have the virus.

Types of Studies Reviewed

The authors searched electronic databases (PubMed, Embase, Web of Science, Google Scholar) for studies focused on dysgeusia, ageusia, and other taste disorders and their relationship to local and systemic causes.

Results

The authors found pertinent literature explaining the normal physiology of taste sensation, proposals for suggested new tastes, presence of gustatory receptors in remote tissues of the body, and etiology and pathophysiology of taste disorders, in addition to the valuable knowledge gained about gustatory disorders in the context of COVID-19. Along with olfactory disorders, taste disorders are one of the earliest suggestive symptoms of COVID-19 infection.

Conclusions

Gustatory disorders are the result of local or systemic etiology or both. Newer taste sensations, such as calcium and fat tastes, have been discovered, as well as taste receptors that are remote from the oropharyngeal area. Literature published during the COVID-19 pandemic to date reinforces the significance of early detection of potential patients with COVID-19 by means of screening for recent-onset taste disorders.

Practical Implications

Timely screening and identification of potential gustatory disorders are paramount for the dental care practitioner to aid in the early diagnosis of COVID-19 and other serious systemic disorders.

Clinical, Prognostic, and Predictive Value of Olfactory Dysfunction for COVID-19: A Prospective Controlled Study

OBJECTIVE

To evaluate the effect of olfactory dysfunction on the course and severity of COVID-19 and its prognostic and predictive significance for COVID-19.

STUDY DESIGN

Prospective case-control study.

SETTING

Ondokuz Mayıs University School of Medicine.

METHODS

Reverse transcription polymerase chain reaction (PCR)-positive patients, patients with COVID-19-related symptoms who had a negative PCR result, and healthy controls were included in the study. Clinicodemographic characteristics, inflammatory markers, and computed tomography stages were recorded. Disease progression and intensive care unit admission were registered. The visual analog scale (0, worst; 10, best) was used to evaluate subjective olfactory, taste, and nasal breathing ability, and the Sniffin' Sticks identification (SS-ID) test was used for psychophysical olfactory assessment.

RESULTS

Mean SS-ID scores were significantly lower in the positive group (8.77) than in the negative (10.43) and healthy control (12.17) groups. VAS-smell scores were significantly lower and anosmia was more prevalent in PCR-positive patients (P < .01). SS-ID and VAS-smell scores were significantly correlated (r = 0.681, P < .001). The inflammatory parameters, pulmonary infiltration stage, disease progression, and ICU admission were not associated with SS-ID scores. A cutoff SS-ID score <9 resulted in 55.56% sensitivity in predicting COVID-19 positivity, and a cutoff VAS-smell score <8 yielded 72.22% sensitivity.

CONCLUSION

Olfactory dysfunction was detected objectively and subjectively in the PCR-positive group, and no difference was found in terms of taste function and nasal breathing. The severity and prognosis of COVID-19 are not exclusively dependent on olfactory dysfunction. The degree of olfactory dysfunction can be useful in predicting PCR positivity.

Self-reported olfactory and gustatory dysfunction and psychophysical testing in screening for Covid-19: A systematic review and meta-analysis

Background

A substantial proportion of coronavirus disease‐2019 (COVID‐19) patients demonstrate olfactory and gustatory dysfunction (OGD). Self‐reporting for OGD is widely used as a predictor of COVID‐19. Although psychophysical assessment is currently under investigation in this role, the sensitivity of these screening tests for COVID‐19 remains unclear. In this systematic review we assess the sensitivity of self‐reporting and psychophysical tests for OGD.

Methods

A systematic search was performed on PubMed, EMBASE, and ClinicalTrials.gov from inception until February 16, 2021. Studies of suspected COVID‐19 patients with reported smell or taste alterations were included. Data were pooled for meta‐analysis. Sensitivity, specificity, and diagnostic odds ratio (DOR) were reported in the outcomes.

Results

In the 50 included studies (42,902 patients), self‐reported olfactory dysfunction showed a sensitivity of 43.9% (95% confidence interval [CI], 37.8%‐50.2%), a specificity of 91.8% (95% CI, 89.0%‐93.9%), and a DOR of 8.74 (95% CI, 6.67‐11.46) for predicting COVID‐19 infection. Self‐reported gustatory dysfunction yielded a sensitivity of 44.9% (95% CI, 36.4%‐53.8%), a specificity of 91.5% (95% CI, 87.7%‐94.3%), and a DOR of 8.83 (95% CI, 6.48‐12.01). Olfactory psychophysical tests analysis revealed a sensitivity of 52.8% (95% CI, 25.5%‐78.6%), a specificity of 88.0% (95% CI, 53.7%‐97.9%), and a DOR of 8.18 (95% CI, 3.65‐18.36). One study used an identification test for gustatory sensations assessment.

Conclusion

Although demonstrating high specificity and DOR values, neither self‐reported OGD nor unvalidated and limited psychophysical tests were sufficiently sensitive in screening for COVID‐19. They were not suitable adjuncts in ruling out the disease.

Taste loss as a distinct symptom of COVID-19: A systematic review and meta-analysis

Chemosensory scientists have been skeptical that reports of COVID-19 taste loss are genuine, in part because before COVID-19, taste loss was rare and often confused with smell loss. Therefore, to establish the predicted prevalence rate of taste loss in COVID-19 patients, we conducted a systematic review and meta-analysis of 376 papers published in 2020-2021, with 241 meeting all inclusion criteria. Additionally, we explored how methodological differences (direct vs. self-report measures) may affect these estimates. We hypothesized that direct prevalence measures of taste loss would be the most valid because they avoid the taste/smell confusion of self-report. The meta-analysis showed that, among 138,897 COVID-19-positive patients, 39.2% reported taste dysfunction (95% CI: 35.34-43.12%), and the prevalence estimates were slightly but not significantly higher from studies using direct (n = 18) versus self-report (n = 223) methodologies (Q = 0.57, df = 1, p = 0.45). Generally, males reported lower rates of taste loss than did females and taste loss was highest in middle-aged groups. Thus, taste loss is a bona fide symptom COVID-19, meriting further research into the most appropriate direct methods to measure it and its underlying mechanisms.

Olfactory and gustatory dysfunctions in SARS-CoV-2 infection: A systematic review

BACKGROUND

Among Coronavirus Disease 2019 (COVID-19) manifestations, Olfactory (OD) and Gustatory (GD) Dysfunctions (OGD) have drawn considerable attention, becoming a sort of hallmark of the disease. Many have speculated on the pathogenesis and clinical characteristics of these disturbances; however, no definite answers have been produced on the topic. With this systematic review, we aimed to collect all the available evidence regarding the prevalence of OGD, the timing of their onset and their resolution, their rate of recovery and their role as diagnostic and prognostic tools for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection.

METHODS

A systematic review comprising all the observational studies that reported the prevalence and/or the longitudinal trajectories of OGD in COVID-19 patients, as self-reported by patients or measured through objective psychophysical tests.

RESULTS

After the selection process, 155 studies were included, with a total of 70,920 patients and 105,291 not-infected individuals. Prevalence reports were extremely variable across studies, with wide ranges for OD (0%-98%) and GD (0-89%) prevalence. OGD occurred early during the disease course and only rarely preceded other symptoms; out of 30 studies with a follow-up time of at least 20 days, only in 5 studies OGD fully resolved in more than 90% of patients. OGD had low sensitivity and high specificity for SARS-CoV-2 infection; accuracy of OD and GD for infection identification was higher than 80% in 10 out of 33 studies and in 8 out of 22 studies considered, respectively. 28 out of 30 studies that studied the association between OGD and disease severity found how OGD were associated with lower rates of severe pneumonia, hospitalization and mortality.

CONCLUSIONS

OGD seem to be highly prevalent in SARS-CoV-2 infection. They occur early, concomitantly with other symptoms and often persist after recovery, in some cases for months; whether a full recovery eventually occurs in all cases is not clear yet. OGD are good predictors of SARS-CoV-2 infection and are associated with a milder disease course.

Objective evaluation of the nasal mucosal secretion in COVID-19 patients with anosmia

BACKGROUND

COVID-19 is a new disease caused by the SARS-CoV-2 virus. The olfactory dysfunction linked to COVID-19 is not associated with rhinorrhea but there is no objective evaluation.

AIMS

To evaluate nasal mucosal secretion objectively in COVID-19 patients with anosmia.

METHODS

Fifty-two COVID-19 patients with anosmia and 51 healthy individuals included. Anosmia was diagnosed by subjective questionnaires. Nasal Schirmer test was done to the left and the right nasal cavity separately.

RESULTS

All patients had anosmia and 82.6% had gustatory dysfunction. In group 1, the mean of the nasal Schirmer test results in the right cavity was 12.4 mm, 12.01 mm in the left nasal cavity. The median wetting distance (right plus left divided by two) was calculated 12.21 mm. In group 2, the mean of the nasal Schirmer test results in the right cavity was 12.1 mm, 11.8 mm in the left nasal cavity. The median wetting distance (right plus left divided by two) was calculated11.97 mm. There was no difference between the two groups in terms of nasal schirmer.

CONCLUSION

Olfactory dysfunction and gustatory dysfunction are the two of the unknown for this disease. We evaluated the nasal mucosa secretions in COVID-19 patients with anosmia objectively to evaluate if there is inflammation in the nasal mucosa. We found no difference between healthy individuals. According to our study, SARS-CoV-2 causes anosmia without causing nasal mucosal inflammation. Invasion of the olfactory bulb and central nervous system by SARS-CoV-2 may lead to anosmia in COVID-19, which may cause olfactory dysfunction.

The prevalence of olfactory and gustatory dysfunction in covid-19 - A systematic review

OBJECTIVES

Loss of smell or taste are early symptoms of COVID-19. Given the high asymptomatic rate of COVID-19, as well as unreliable temperature checking and contact history taking, it is important to understand the role of olfactory and gustatory dysfunction (OGD) in the diagnosis of COVID-19. The aim of this study is to determine how initial symptoms of OGD can be used to screen patients for COVID-19 laboratory testing.

METHODS

We followed recommendations from the Preferred Reporting Items for Systemic Reviews and Meta-analysis (PRISMA) statement to conduct this systematic review study. We used OGD-related key words to search for literature published between January 1, 2020 and September 30, 2020 on Pubmed, Ovid Medline databases. We estimated the prevalence of OGD and compared it with that of other OGD-related symptoms. The weighted summary proportion under the fixed and random effects model was assessed using MedCalc statistical software. Whenever there was heterogeneity, a random effects model was selected. Publication bias was assessed by funnel plot asymmetry and Egger's regression test.

RESULTS

A total of 25 articles (evidence level III:5; IV:20) were identified and reviewed. Data synthesis of 19 articles revealed that the pooled prevalence of olfactory dysfunction in COVID-19 is 53.56% (range 5.6-100%, 95% CI 40.25-66.61%). The pooled prevalence of gustatory dysfunction in COVID-19 is 43.93% (range 1.5-85.18%, 95% CI 28.72-59.74%), just behind fever (62.22%, range 18.18-95.83%, 95% CI 54.82-69.33%), cough (64.74%, range 38.89-87.5%, 95% CI 57.97-71.22%), and fatigue (56.74%, range 6.25-93.62%, 95% CI 32.53-79.35%). The prevalence of gustatory dysfunction in subgroup with objective evaluation is lower than those without (9.91% vs. 49.21%, relive risk 2.82, p<0.001).

CONCLUSION

Our updated systematic review attests that OGD is an important early symptom of COVID-19 infection. Screening for OGD should be further emphasized to prioritize patients for laboratory test.

Taste alteration in COVID-19: Significant geographical differences exist in the prevalence of the symptom

Early detection of COVID-19 is important for reduction in the spread of the disease and gustatory disturbances (GD) are known to have a strong predictive value. In the present study, we aimed to map the geographical differences in the prevalence of GD in individuals infected with SARS-CoV-2 during the first wave of COVID-19 in order to improve case identification and to facilitate prioritization. We undertook a rapid scoping review of articles published in the repository of the National Library of Medicine (MEDLINE/PubMed) and medRxiv from their inception until 3^rd September, 2020. The minimum requirements for completing a restricted systematic review were fulfilled. Of the 431 articles retrieved, 61 studies (28,374 cases confirmed with COVID-19) from 20 countries were included in the analysis. GD were most prevalent in the Americas [66.78%, 95% CI 54.77–78.79%] compared to Europe [57.18%, 95% CI 52.35–62.01%], the Middle East [38.83%, 95% CI 27.47–50.19%] and East Asia [13.1%, 95% CI 0.14–26.06%]. No differences of GD prevalence were evident between February and August 2020. The data demonstrate that there is a marked geographical distribution of GD in COVID-19 patients which, possibly, might be explained by differences in diagnostic criteria for COVID-19 case definition during the early phase of the pandemic.

Olfactory and taste dysfunctions in COVID-19

PURPOSE OF REVIEW

Olfactory dysfunction (OD) can be a single and early prominent symptom of severe acute respiratory syndrome (SARS)-COV-2 infection unlike middle east respiratory syndrome (MERS) and SARS. OD data are very informative but many are not peer-reviewed, often inconclusive and may reveal variable and sometimes contradictory results. This is often due to incongruent data of subjective and objective OD testing. Mechanistic pathways of OD and taste dysfunction (TD) are slowly unveiling, not infrequently extrapolated from historical models of SARS and MERS and are still partly unclear.

RECENT FINDINGS

We reviewed the literature on OD and TD during the COVID-19 pandemic analyzing current data on pathogenesis and clinical correlates including prevalence, recovery rates, risk factors, and predictive power. Also, we evaluated various methods of subjective and objective olfactory testing and discussed challenges in management of patients with OD and rhinitis during the pandemic.

SUMMARY

Subjective evaluation of smell disturbances during COVID-19 pandemic likely underestimates true prevalence, severity, and recovery rates of OD when compared to objective testing. OD is predictive of COVID-19 infection, more so when associated with TD. Recognizing inherent limitations of both subjective and objective OD and TD testing enables us better to manage chemosensory dysfunction in COVID-19 patients. Besides, current mechanistic data suggest neurotropism of COVID-19 for olfactory neuro-epithelium and a potential role of transient receptor potential (TRP) channels. Future studies are needed to explore further the neurogenic inflammation in COVID-19.

Alteration of Smell Sensation: Brief Review With Implications for Nursing Care During the COVID-19 Pandemic

ABSTRACT

BACKGROUND: Alteration in olfaction, the sense of smell, can lead to a surprisingly high level of functional disability. Effects can range from mild changes in nutrient intake to a significant decrease in quality of life. Olfactory dysfunction can follow clinical problems such as trauma to the brain and nose. During recent months, in the setting of the current worldwide pandemic of coronavirus disease 2019 (COVID-19), the infection caused by severe acute respiratory syndrome coronavirus 2, it has become clear that olfaction can also be damaged by viruses that enter the body through the nose. METHODS: To learn more about this important clinical problem, we reviewed the current literature about smell sensation and the contextual application of altered olfaction in the setting of COVID-19. Knowledge about this topic, along with other clinical aspects of COVID-19, is expanding quickly. CONCLUSION: Nurses perform assessments, assist with implementing treatment interventions, and provide vital education to patients and their families. These interventions help patients with olfactory dysfunction achieve the best possible functional outcome.

Smell and Taste Disturbance in COVID-19 Patients: A Prospective Multicenteric Review

To study the incidence of the smell and taste disturbance in the COVID-19 patients and a follow up at 4 months to observe for the duration of resolution of these symptoms. This is a multicentric prospective study carried out in 3 different countries, from April, 2020 to January, 2021. The COVID-19 positive patients, aged between 15 and 60 years, were inquired about the presence of any smell or taste related symptoms. The same patients were followed up with the telephonic interview after 2 months and then after 4 months, respectively. The duration of resolution of the smell and taste disturbance symptoms was noted. Total of 188 COVID-19 positive patients, average age 33.1 ± 1.7 years, 54.2% males and 45.8% female were included in the study. The smell disturbance was present in 60.6% (hyposmia 36.1%, anosmia 20.2%, and parosmia 4.2%) and taste disturbance in 28.7% of patients (hypogeusia 20.2%, ageusia 6.9%, and parageusia 1.6%). There was improvement of anosmia by 97.4, hyposmia by 95.6%, parosmia by 100%, ageusia by 100%, hypogeusia 94.8%, and parageusia by 66.7%, at 4 months follow up. The present study concludes that the smell and taste disturbances are one of the main early presenting features of the COVID-19 infection. The temporary effect of the COVID-19 infection on the olfactory and gustatory pathway was also highlighted with more than 95% patients improving at 4 months of follow up.

Prevalence of Olfactory Dysfunction in Coronavirus Disease 2019 (COVID-19): A Meta-analysis of 27,492 Patients

OBJECTIVES/HYPOTHESIS

Olfactory dysfunction has been observed as one of the clinical manifestations in COVID-19 patients. We aimed to conduct a systematic review and meta-analysis to estimate the overall pooled prevalence of olfactory dysfunction in COVID-19 patients.

STUDY DESIGN

Systematic review and meta-analyses.

METHODS

PubMed, Scopus, Web of Science, Embase, and Google Scholar databases were searched to identify studies published between 1 December 2019 and 23 July 2020. We used random-effects model to estimate the pooled prevalence with 95% confidence intervals (CIs). Heterogeneity was assessed using the I2 statistic and Cochran's Q test. Robustness of the pooled estimates was checked by different subgroup and sensitivity analyses This study is registered with PROSPERO (CRD42020183768).

RESULTS

We identified 1162 studies, of which 83 studies (n = 27492, 61.4% female) were included in the meta-analysis. Overall, the pooled prevalence of olfactory dysfunction in COVID-19 patients was 47.85% [95% CI: 41.20-54.50]. We observed olfactory dysfunction in 54.40% European, 51.11% North American, 31.39% Asian, and 10.71% Australian COVID-19 patients. Anosmia, hyposmia, and dysosmia were observed in 35.39%, 36.15%, and 2.53% of the patients, respectively. There were discrepancies in the results of studies with objective (higher prevalence) versus subjective (lower prevalence) evaluations. The discrepancy might be due to false-negative reporting observed in self-reported health measures.

CONCLUSIONS

The prevalence of olfactory dysfunction in COVID-19 patients was found to be 47.85% based on high-quality evidence. Due to the subjective measures of most studies pooled in the analysis, further studies with objective measures are advocated to confirm the finding.

LEVEL OF EVIDENCE

2 Laryngoscope, 131:865-878, 2021.

Long-term follow-up of olfactory and gustatory dysfunction in COVID-19: 6 months case-control study of health workers

PURPOSE

The study aimed to determine the incidence and long-term evolution of COVID-related olfactory (OD) and gustatory (GD) dysfunction, the recovery timeline, and the association with other symptoms. The secondary objective was to identify the predictive clinical factors for the evolution of these symptoms.

METHODS

A prospective case-control study was conducted from March 15 to October 15, 2020, in health workers with COVID-19 related symptoms in a tertiary care hospital. 320 patients were included after 6 months of follow-up: 195 in the case group and 125 in the control group. Olfactory dysfunction (OD), dysosmia, and gustatory dysfunction (GD) onset and recovery rate after 6 months follow-up are analyzed in both groups.

RESULTS

There were 125 (64.1%) in case group patients with OD and 118 (60.5%) with GD. Total or partial recovery OD and GD was found in 89%, mainly in the first 2 months. In the control group, there were 14 (11.2%) patients with OD and 33 (26.4%) patients with GD, with 100% of total/partial recovery.

CONCLUSION

In both groups, OD and GD showed high-resolution rates during the first two months after the onset of symptoms. Nevertheless, 11% of the case group patients did not show any recovery, and the partial resolution was present in 30% of our patients, at the 6 months follow-up. We found a high correlation between OD and GD, both in the appearance of symptoms and in their recovery. Nasal obstruction and dyspnea have been identified as risk factors for the persistence of symptoms.

Oral Symptoms Associated with COVID-19 and Their Pathogenic Mechanisms: A Literature Review

Since the worldwide spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, management of coronavirus disease 2019 (COVID-19) has been challenging for healthcare providers. The oral cavity is referred to as a target of SARS-CoV-2. The aim of this study was to review oral symptoms specific to COVID-19 patients from the point of view of symptom prevalence and pathogenesis and to speculate the pathogenic mechanisms underlying them. Scientific articles were retrieved by searching PubMed/MEDLINE, Google Scholar, medRxiv, and bioRxiv from 3 February 2020 to 31 December 2020, and they were reviewed by title, abstract, and text for relevance. The literature search indicated that COVID-19 patients frequently present with gustatory dysfunction, xerostomia, and oral mucosal lesions, while their prevalence is likely to vary by country, age, gender, and disease severity. Gustatory dysfunction and xerostomia appear at an early stage of SARS-CoV-2 infection and last relatively long. One of possible pathogenic mechanisms of both symptoms is attributed to the expression of viral cellular entry-relevant receptors in taste cells and salivary glands. Dental professionals who can first become aware of oral symptoms associated with COVID-19 will play a more active role in and make a greater contribution to diagnosis and prevention of COVID-19.

Onset and duration of symptoms of loss of smell/taste in patients with COVID-19: A systematic review

Objective

The aim of the study was to conduct a systematic review of the literature to investigate the time of onset and duration of symptoms of loss of smell and taste in patients diagnosed with COVID-19.

Methods

Two independent authors performed a systematic review of the Medline/PubMed, SCOPUS, COCHRANE, Lilacs and Web of Science electronic databases. The time of onset and duration of symptoms were considered primary outcomes. The sex and age of individuals, the geographical location of the study, the prevalence of symptoms, other associated symptoms, associated comorbidities, and the impact on quality of life and eating habits were considered secondary outcomes.

Results

Our search generated 17 articles. Many of the studies reported that the onset of anosmia and ageusia occurred 4 to 5 days after the manifestation of other symptoms of the infection and that these symptoms started to disappear after one week, with more significant improvements in the first two weeks.

Conclusion

The present study concludes that the onset of symptoms of loss of smell and taste, associated with COVID-19, occurs 4 to 5 days after other symptoms, and that these symptoms last from 7 to 14 days. Findings, however, varied and there is therefore a need for further studies to clarify the occurrence of these symptoms. This would help to provide early diagnosis and reduce contagion by the virus.

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

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.

Regional and Chronological Variation of Chemosensory Dysfunction in COVID-19: a Meta-Analysis

BACKGROUND

Olfactory and gustatory dysfunction are frequently reported in patients with coronavirus disease 2019 (COVID-19). However, the reported prevalence of olfactory and/or gustatory dysfunction varies widely, and the reason for the inter-study differences is unclear. Hence, in this meta-analysis, we performed subgroup analyses to investigate the factors that contribute to the inter-study variability in the prevalence of olfactory and gustatory dysfunction.

METHODS

Out of 943 citations, we included 55 eligible studies with 13,527 patients with COVID-19 for a meta-analysis. Calculating the data extracted from each study, the weighted summary prevalence of olfactory and gustatory dysfunction was estimated using a Freeman-Tukey transformation with models based on random-effects assumptions. A meta-analysis of variance compared the prevalence of olfactory and gustatory dysfunction according to regional, chronological, demographic, and methodologic factors, respectively.

RESULTS

The overall pooled prevalence rates of olfactory and gustatory dysfunction were 51.4% and 47.5%, respectively, in the random-effect model. In subgroup analyses, the prevalence rates of olfactory and gustatory dysfunction were significantly different among four geographical regions (both P < 0.001, respectively). Although the prevalence rates of olfactory and gustatory dysfunction did not significantly differ according to the time of enrollment, the subgroup analyses including only studies from the same geographical region (Europe) revealed a significant difference in olfactory dysfunction according to the time of enrollment.

CONCLUSION

The regional and chronological differences in the prevalence rates of olfactory and gustatory dysfunctions partly explain the wide inter-study variability.

Olfactory Dysfunction in COVID-19 Patients: Findings from a Tertiary Rural Centre

Olfactory and/or taste dysfunction are potential neurological manifestations of coronavirus disease -2019 (COVID-19). The aim of the study was to document the prevalence of anosmia in COVID-19 positive patients and analyze the effect of various factors on the occurrence of these chemosensory dysfunction in the local population. Tertiary referral center. Prospective Study. 250 subjects who tested positive for SARS-CoV-2, by real-time polymerase chain reaction (RT-PCR) and admitted in Isolation ward were enrolled for the study. Data was collected from the subjects via oral questionnaire method, based on the AAO-HNS Anosmia Reporting Tool. Data was collected regarding the age, gender, olfactory or gustatory disturbances, history of recent travel or contact with a positive case, smoking, any associated symptoms, any co-morbid conditions and recovery time of sense of olfaction. Out of 250, 179 (71.6%) subjects were diagnosed with Olfactory dysfunction out of which majority were males, 105 (58.6%). Most of the patients were above 40 years of age (n = 184, 73.6%). Majority of the individuals (88 patients) had close contact with a positive case in recent past, followed by 67 patients who were health care workers, hence proving that risk of infection increases with exposure. Anosmia was present in 68.5% of all the 127 non-smokers. 66.4% had both olfactory as well as gustatory dysfunction whereas 18 patients (7.2%) were found to be totally asymptomatic. Mostly patients recovered their sense of smell within 1-2 weeks from the day of onset of anosmia. Presence of olfactory dysfunction of any degree with or without alteration in taste sensation should raise a suspicion of COVID-19 infection, especially when other classical signs are not present. In such conditions, swabs should be sent for confirmation by RT-PCR testing and till results are awaited, the individual should be shifted to quarantine facilities or advised strict self-isolation.

Clinical Olfactory Working Group consensus statement on the treatment of postinfectious olfactory dysfunction

BACKGROUND

Respiratory tract viruses are the second most common cause of olfactory dysfunction. As we learn more about the effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with the recognition that olfactory dysfunction is a key symptom of this disease process, there is a greater need than ever for evidence-based management of postinfectious olfactory dysfunction (PIOD).

OBJECTIVE

Our aim was to provide an evidence-based practical guide to the management of PIOD (including post-coronavirus 2019 cases) for both primary care practitioners and hospital specialists.

METHODS

A systematic review of the treatment options available for the management of PIOD was performed. The written systematic review was then circulated among the members of the Clinical Olfactory Working Group for their perusal before roundtable expert discussion of the treatment options. The group also undertook a survey to determine their current clinical practice with regard to treatment of PIOD.

RESULTS

The search resulted in 467 citations, of which 107 articles were fully reviewed and analyzed for eligibility; 40 citations fulfilled the inclusion criteria, 11 of which were randomized controlled trials. In total, 15 of the articles specifically looked at PIOD whereas the other 25 included other etiologies for olfactory dysfunction.

CONCLUSIONS

The Clinical Olfactory Working Group members made an overwhelming recommendation for olfactory training; none recommended monocycline antibiotics. The diagnostic role of oral steroids was discussed; some group members were in favor of vitamin A drops. Further research is needed to confirm the place of other therapeutic options.

Clinical significance of smell and taste dysfunction and other related factors in COVID-19

PURPOSE

The objective of this study is to evaluate smell and taste dysfunction (STD) in coronavirus disease 2019 (COVID-19) positive and negative patients, and to assess the factors associated with STD in COVID-19 positive patients.

METHODS

Patients who had been tested with the real-time reverse transcriptase-polymerase chain reaction (RT-PCR) for COVID-19 were identified, and according to the RT-PCR test results, patients were separated into Positive and Negative Groups. A telephone-based assessment was applied to both groups using the American Academy of Otolaryngology-Head and Neck Surgery Anosmia Reporting Tool. Patients in Positive Group were also asked to rate STD, nasal breathing, and anxiety in three different time periods (pre-/during-/post-COVID) using the visual analog scale (VAS).

RESULTS

A total of 53 COVID-19 positive and 51 negative patients completed the surveys. STD was eightfold more frequent (OR 8.19; CI 95% 3.22-20.84) in the Positive Group. Of the 53 COVID-19 positive patients, 32 reported STD and 21 did not. 'Ground-glass appearance' on chest-computed tomography was more frequent and median lymphocyte count was significantly lower in COVID-19 positive patients with STD. During-COVID STD and nasal breathing VAS scores were significantly lower than the pre- and post-COVID scores. During-COVID STD scores were significantly correlated with anxiety scores (Spearman's rho-0.404, p = 0.022) but not correlated with nasal breathing scores.

CONCLUSION

STD may be related to increased inflammatory response as well as damage of olfactory neuronal pathway or non-neuronal olfactory mucosa. Understanding the exact cause of chemosensory impairment in COVID-19 can be helpful in explaining the pathophysiology of the disease.

Prevalence and Characteristics of Taste Disorders in Cases of COVID-19: A Meta-analysis of 29,349 Patients

OBJECTIVE

The purpose of this meta-analysis is to assess the pooled prevalence of taste disorders and their subtypes in patients with COVID-19.

DATA SOURCES

PubMed, Scopus, Web of Science, Embase, and Google Scholar databases were searched to identify studies published between December 1, 2019, and June 23, 2020, without language restrictions. There was no restriction on the study design; therefore, observational studies, clinical trials, and case series were included. In addition, preprints were considered if data of interest were reported.

REVIEW METHODS

Two authors independently screened articles for eligibility. A random effects model was used to estimate the pooled prevalence with 95% CIs. Quality assessment was done with critical appraisal tools of the Joanna Briggs Institute. The robustness of the pooled estimates was checked by subgroup and sensitivity analyses.

RESULTS

Fifty-nine studies were included (N = 29,349 patients, 64.4% female). The pooled prevalence of taste disorders in patients with COVID-19 was 48.1% (95% CI, 41.3%-54.8%). The prevalence of taste disorders in studies with objective assessments was higher as compared with subjective assessments (59.2% vs 47.3%). The disorders were observed in 55.2% of European patients; 61.0%, North American; 27.1%, Asian; 29.5%, South American; and 25.0%, Australian. Ageusia, hypogeusia, and dysgeusia were detected in 28.0%, 33.5%, and 41.3% of patients with COVID-19. We identified 91.5% of the included studies as high quality.

CONCLUSIONS

The prevalence of taste disorders in patients with COVID-19 was 48.1%. Objective assessments have higher prevalence than subjective assessments. Dysgeusia is the most common subtype, followed by ageusia and hypogeusia.

SARS-CoV-2, ACE2 expression, and systemic organ invasion

A novel coronavirus disease, COVID-19, has created a global pandemic in 2020, posing an enormous challenge to healthcare systems and affected communities. COVID-19 is caused by severe acute respiratory syndrome (SARS)-coronavirus-2 (CoV-2) that manifests as bronchitis, pneumonia, or a severe respiratory illness. SARS-CoV-2 infects human cells via binding a "spike" protein on its surface to angiotensin-converting enzyme 2 (ACE2) within the host. ACE2 is crucial for maintaining tissue homeostasis and negatively regulates the renin-angiotensin-aldosterone system (RAAS) in humans. The RAAS is paramount for normal function in multiple organ systems including the lungs, heart, kidney, and vasculature. Given that SARS-CoV-2 internalizes via ACE2, the resultant disruption in ACE2 expression can lead to altered tissue function and exacerbate chronic diseases. The widespread distribution and expression of ACE2 across multiple organs is critical to our understanding of the varied clinical outcomes of COVID-19. This perspective review based on the current literature was prompted to show how disruption of ACE2 by SARS-CoV-2 can affect different organ systems.

Evaluation of predictive value of olfactory dysfunction, as a screening tool for COVID-19

OBJECTIVES

At the end of 2019, SARS-CoV-2 was identified, the one responsible for the COVID-19 disease. Between a 5.1% and a 98% of COVID-19 patients present some form of alteration in their sense of smell. The objective of this study is to determine the diagnostic yield of the smell dysfunction as screening tool for COVID-19.

METHODS

Cross-sectional, observational, and pro-elective study was performed in a tertiary care hospital from May 25th to June 30th, 2020. One hundred and thirty-nine patients were included in the study. Demographic characteristics were collected from anamnesis. A Self-Perception Questionnaire and psychophysical olfactory test (POT) were applied to all participants. The presence of SARS-CoV2, was detected by RT-PCR methods.

RESULTS

51.7% of patients were SARS-CoV-2 positive. A sensitivity of 50% was obtained for the self-perception questionnaire as a screening tool for SARS-CoV2, with a specificity of 80.59%. The positive predictive value (PPV) was of 73.46%, the negative predictive value (NPV) was of 60%. The POT as a screening tool had a PPV of 82.35%, a NPV of 52.45%, a LR+ of 4.34, a LR- 0.84. The combination of anosmia (according to the POT) plus cough and asthenia got an OR of 8.25 for the SARS CoV-2 infection.

CONCLUSION

There is a strong association between olfactory dysfunction and COVID-19. However, it is not really efficient in the screening of SARS-CoV-2 infection and thus, they should not be considered as a single diagnostic instrument.

LEVEL OF EVIDENCE

4.

Taste and Smell Impairment in Critically Ill Patients With COVID-19: An Intensive Care Unit Study

OBJECTIVE

To determine taste and smell impairment rates in patients with coronavirus disease 2019 (COVID-19) who were hospitalized in the intensive care unit (ICU).

METHODS

Between March 2020 and May 2020, patients with COVID-19 hospitalized in the ICU were enrolled in this study. Upon discharge, patients were telephoned and asked to complete a survey related to taste and smell impairment. Characteristics were compared between patients with and without taste and/or smell impairment.

RESULTS

Fifty-two patients were enrolled (mean age, 61.32 ± 12.53 years; mean ICU stay, 10.19 ± 10.24 days). Age, sex, type/number of comorbid diseases, most ICU support modalities, and ICU stay duration did not significantly differ between groups. Patients in group B required more high-flow nasal oxygen therapy than patients in group A (P = .010). In total, 22 (42.3%) of 52 patients experienced taste and/or smell impairment. Three patients experienced isolated smell impairment and one patient experienced isolated taste impairment. Among the 21 patients who experienced smell impairment, 18 (85.78%) experienced hyposmia (mean visual analog scale [VAS] score: 6.33 ± 0.97), while 3 (14.28%) experienced anosmia. Among the 19 patients who experienced taste impairment, 16 (84.22%) experienced hypogeusia (mean VAS score: 6.43 ± 1.03) and 3 (15.78%) experienced ageuisa. Among 22 patients who experienced taste and/or smell impairment, 15 (68.18%) patients (n = 15/22) experienced smell and/or taste impairment before the ICU stay, while 7 (31.82%) patients (n = 7/22) experienced impairment during the ICU stay. Overall, 28.84% (n = 15/52) of the patients experienced taste and/or smell impairment before the ICU stay.

CONCLUSIONS

Patients who were hospitalized in the ICU experienced lower rates of taste and/or smell impairment. Some patients experienced taste and/or smell impairment during the ICU stay.

Coronavirus Disease-19 and Rhinology/Facial Plastics

This review summarizes the challenges and adaptations that have taken place in rhinology and facial plastics in response to the ongoing coronavirus disease-19 pandemic. In particular, the prolonged exposure and manipulation of the nasal and oral cavities portend a high risk of viral transmission. We discuss evidence-based recommendations to mitigate the risk of viral transmission through novel techniques and device implementation as well as increasing conservative management of certain pathologies.

Anosmia/Hyposmia is a Good Predictor of Coronavirus Disease 2019 (COVID-19) Infection: A Meta-Analysis

Introduction  The number of positive cases and deaths from the coronavirus disease 2019 (COVID-19) is still increasing. The early detection of the disease is very important. Olfactory dysfunction has been reported as the main symptom in part of the patients.

Objective  To analyze the potential usefulness of anosmia or hyposmia in the detection of the COVID-19 infection.

Data Synthesis  We systematically searched the PubMed Central database using specific keywords related to our aims until July 31st, 2020. All articles published on COVID-19 and anosmia or hyposmia were retrieved. A statistical analysis was performed using the Review Manager (RevMan, Cochrane, London, UK) software, version 5.4. A total of 10 studies involving 21,638 patients were included in the present analysis. The meta-analysis showed that anosmia or hyposmia is significantly associated with positive COVID-19 infections (risk ratio [RR]: 4.56; 95% confidence interval [95%CI]: 3.32–6.24; p  < 0.00001; I ²  = 78%, random-effects modeling).

Conclusion  The presence of anosmia or hyposmia is a good predictor of positive COVID-19 infections. Patients with onset of anosmia or hyposmia should take the test or undergo screening for the possibility of COVID-19 infection.

Ear nose throat-related symptoms with a focus on loss of smell and/or taste in COVID-19 patients

Purpose

To determine the frequency and severity of general and ear nose throat (ENT)- related symptoms, especially smell and/or loss of sense of taste (STL) in COVID-19 disease, as well as to investigate the recovery process of STL.

Materials and methods

Patients with a positive COVID-19 diagnosis were given a questionnaire consisting of general questions (age, sex, date of symptoms, smoking history, concomitant diseases), questions about the most obvious symptom at presentation (one option only), the severity and frequency of symptoms (general and ENT), and STL (recovery time and degree of recovery).

Results

The study population consisted of 172 patients, 18–65 years old (mean age, 37.8 ± 12.5 years; 51.2% female; 76.2% nonsmokers). Cough (n = 30, 17.4%) and loss of sense of smell (n = 18, 10.4%) were the most obvious general and ENT symptoms, respectively. Eighty-eight patients (51.2%) reported loss of sense of smell, and 81 patients (47.1%) reported loss of sense of taste. The mean recovery times for loss of sense of smell and loss of sense of taste were 8.02 ± 6.41 and 8.20 ± 7.07 days, respectively. The loss of sense of smell and loss of sense of taste were the unique symptoms in four (4.54%) and one (1.23%) patients, respectively.

Conclusion

STL is a common symptom in COVID-19 and may be the first and/or only symptom of this disease. In patients presenting with STL complaints, surveillance for possible COVID-19 disease and screening tests will facilitate the struggle against the disease.

Neuromuscular presentations in patients with COVID-19

COVID-19 is caused by the coronavirus SARS-CoV-2 that has an affinity for neural tissue. There are reports of encephalitis, encephalopathy, cranial neuropathy, Guillain-Barrè syndrome, and myositis/rhabdomyolysis in patients with COVID-19. In this review, we focused on the neuromuscular manifestations of SARS-CoV-2 infection. We analyzed all published reports on SARS-CoV-2-related peripheral nerve, neuromuscular junction, muscle, and cranial nerve disorders. Olfactory and gustatory dysfunction is now accepted as an early manifestation of COVID-19 infection. Inflammation, edema, and axonal damage of olfactory bulb have been shown in autopsy of patients who died of COVID-19. Olfactory pathway is suggested as a portal of entry of SARS-CoV-2 in the brain. Similar to involvement of olfactory bulb, isolated oculomotor, trochlear and facial nerve has been described. Increasing reports Guillain-Barrè syndrome secondary to COVID-19 are being published. Unlike typical GBS, most of COVID-19-related GBS were elderly, had concomitant pneumonia or ARDS, more prevalent demyelinating neuropathy, and relatively poor outcome. Myalgia is described among the common symptoms of COVID-19 after fever, cough, and sore throat. Duration of myalgia may be related to the severity of COVID-19 disease. Few patients had muscle weakness and elevated creatine kinase along with elevated levels of acute-phase reactants. All these patients with myositis/rhabdomyolysis had severe respiratory complications related to COVID-19. A handful of patients with myasthenia gravis showed exacerbation of their disease after acquiring COVID-19 disease. Most of these patients recovered with either intravenous immunoglobulins or steroids.

Frequency and Clinical Utility of Olfactory Dysfunction in COVID-19: a Systematic Review and Meta-analysis

Background

Olfactory dysfunction (OD) has been gaining recognition as a symptom of COVID-19, but its clinical utility has not been well defined.

Objectives

To quantify the clinical utility of identifying OD in the diagnosis of COVID-19 and determine an estimate of the frequency of OD amongst these patients.

Methods

PubMed was searched up to 1 August 2020. Meta-analysis A included studies if they compared the frequency of OD in COVID-19 positive patients (proven by reverse transcription polymerase chain reaction) to COVID-19 negative controls. Meta-analysis B included studies if they described the frequency of OD in COVID-19 positive patients and if OD symptoms were explicitly asked in questionnaires or interviews or if smell tests were performed.

Results

The pooled frequency of OD in COVID-19 positive patients (17,401 patients, 60 studies) was 0.56 (0.47–0.64) but differs between detection via smell testing (0.76 [0.51–0.91]) and survey/questionnaire report (0.53 [0.45–0.62]), although not reaching statistical significance (p = 0.089). Patients with reported OD were more likely to test positive for COVID-19 (diagnostic odds ratio 11.5 [8.01–16.5], sensitivity 0.48 (0.40 to 0.56), specificity 0.93 (0.90 to 0.96), positive likelihood ratio 6.10 (4.47–8.32) and negative likelihood ratio 0.58 (0.52–0.64)). There was significant heterogeneity amongst studies with possible publication bias.

Conclusion

Frequency of OD in COVID-19 differs greatly across studies. Nevertheless, patients with reported OD were significantly more likely to test positive for COVID-19. Patient-reported OD is a highly specific symptom of COVID-19 which should be included as part of the pre-test screening of suspect patients.