Mechanisms of COVID-19-associated olfactory dysfunction.

Olfactory dysfunction is one of the most common symptoms of COVID-19. In the first 2 years of the pandemic, it was frequently reported, although its incidence has significantly decreased with the emergence of the Omicron variant, which has since become the dominant viral strain. Nevertheless, many patients continue to suffer from persistent dysosmia and dysgeusia, making COVID-19-associated olfactory dysfunction an ongoing health concern. The proposed pathogenic mechanisms of COVID-19-associated olfactory dysfunction are complex and likely multifactorial. While evidence suggests that infection of sustentacular cells and associated mucosal inflammation may be the culprit of acute, transient smell loss, alterations in other components of the olfactory system (e.g., olfactory receptor neuron dysfunction, olfactory bulb injury and alterations in the olfactory cortex) may lead to persistent, long-term olfactory dysfunction. This review aims to provide a comprehensive summary of the epidemiology, clinical manifestations and current understanding of the pathogenic mechanisms of COVID-19-associated olfactory dysfunction.

Identifying candidate genes underlying isolated congenital anosmia.

An estimated 1 in 10 000 people are born without the ability to smell, a condition known as congenital anosmia, and about one third of those people have non-syndromic, or isolated congenital anosmia (ICA). Despite the significant impact of olfaction for our quality of life, the underlying causes of ICA remain largely unknown. Using whole exome sequencing (WES) in 10 families and 141 individuals with ICA, we identified a candidate list of 162 rare, segregating, deleterious variants in 158 genes. We confirmed the involvement of CNGA2, a previously implicated ICA gene that is an essential component of the olfactory transduction pathway. Furthermore, we found a loss-of-function variant in SREK1IP1 from the family gene candidate list, which was also observed in 5% of individuals in an additional non-family cohort with ICA. Although SREK1IP1 has not been previously associated with olfaction, its role in zinc ion binding suggests a potential influence on olfactory signaling. This study provides a more comprehensive understanding of the spectrum of genetic alterations and their etiology in ICA patients, which may improve the diagnosis, prognosis, and treatment of this disorder and lead to better understanding of the mechanisms governing basic olfactory function.

Long-term smell loss experiences after COVID-19: A qualitative study.

OBJECTIVES: Sudden smell loss is one of the early symptoms of COVID-19. Although it is stated that the loss of smell and taste following COVID-19 improves within a few weeks, there are also cases that do not improve for a long time. The aim of this study is to reveal long-term smell loss experiences after COVID-19. METHODS: A qualitative approach was adopted. We conducted semistructured interviews with 11 participants who had smell loss for at least 3 months. Interviews were recorded, transcribed and evaluated using a thematic analysis for qualitative data. RESULTS: Nutrition and appetite, personal hygiene, threats to safety and emotional changes were the main themes created by the authors and were the areas where participant expressions focused. The participants used oral/nasal corticosteroid therapy for smell loss and received short-term olfactory training, but could not find a solution. CONCLUSIONS: Long-term smell loss problems, which were neglected during the pandemic period, should be carefully evaluated due to their negative effects. Understanding and focusing on the negative effects of loss of smell may contribute to the solution of long-term smell loss problems. PATIENT AND PUBLIC CONTRIBUTION: Eleven participants who experienced long-term loss of smell following COVID-19 contributed to the study. They enriched the study by describing the effects of their experiences. There was no other participation or contribution from the public to the research.

Four odorants for olfactory training are enough: a pilot study.

BACKGROUND:  Olfactory training (OT) is commonly used for the treatment of olfactory disorders. Nevertheless, there is an ongoing debate about the most effective OT regimen. We aimed to compare the effects of OT with 7 items (rose, lemon, eucalyptus, cloves, stewed apple, balm, mint) to 4-item-OT (rose, lemon, eucalyptus, cloves) over 3 months. Methods: Participants were 40 patients with olfactory dysfunction receiving 4-item-OT or 7-item-OT and 60 gender- and age-matched individuals with normal sense of smell receiving no OT, 4-item-OT, or 7-item-OT. Before and after the OT we assessed n-butanol odor thresholds, discrimination, and identification (TDI score), additionalthresholds for (R)-(-)-carvone, ß-damascenone, salicyclic acid benzylester, the degree of phantosmia and parosmia, cognitive function, and ratings of olfactory function. Results: In both patient groups, the TDI score increased with the use of OT, regardless of the number of odors used (p < 0.001; 3.48 ± 4.21 and lower than control groups). The clinically significant increase of 5.5 points in TDI score correlated with change of ratings of parosmia (r 0.62; p < 0.01) and with ratings of olfactory dysfunction (r = 0.51; p < 0.05). CONCLUSION:  Concluding, OT over a 3-months period with 4 or 7 odors appears to produce similar results, although the sample size has to be considered.

A Study on the Impact of the COVID-19 Pandemic on the Aetiology of Paediatric Olfactory Dysfunction.

INTRODUCTION: Although previous studies have examined olfactory dysfunction in children, the novel coronavirus SARS-CoV-2 has certainly had an unprecedented effect on their olfaction, which could not be taken into consideration. The aim of this report was to present data on the epidemiology of olfactory dysfunction during the pandemic and compare this dataset with a pre-pandemic set. We hypothesized an increase in URTI-related olfactory dysfunction. METHODS: Data of paediatric patients consulting a smell and taste clinic between March 2020 and June 2022 were retrospectively analysed. The frequency of major causes of olfactory dysfunction was examined and compared with three subsets of an older dataset. RESULTS: A total of 52 patients were included in the analysis. Most children presented with olfactory dysfunction due to upper respiratory tract infection (URTI) (52%). Congenital olfactory dysfunction was present in 34% of cases. Sinonasal disorders and idiopathic cases accounted for 6 and 4%, respectively, whereas head trauma was the least common cause (2%). This was in contrast with the results of the older set. The frequency of URTI-related olfactory dysfunction increased significantly. The frequency of head-trauma-related or congenital olfactory dysfunction showed marked reductions. There were no significant differences regarding the other aetiologies between our patient cohort and the three subsets. CONCLUSION: The COVID-19 pandemic has resulted in differences regarding the prevalence of aetiologies between our dataset and the subsets of pre-pandemic times. The surge of the frequency of URTI-related olfactory dysfunction may be ascribed to a novel pathomechanism involving sustentacular cells in the olfactory epithelium.

Corticosteroid nasal irrigation as early treatment of olfactory dysfunction in COVID-19: A prospective randomised controlled trial.

OBJECTIVE: This study aimed to evaluate the efficacy of corticosteroid irrigation compared to saline to no nasal irrigation in COVID-19 patients with olfactory loss. DESIGN AND SETTING: A randomised controlled study was conducted at the Otolaryngology-Head & Neck Surgery Department, Ramathibodi Hospital, Faculty of Medicine, Mahidol University. PARTICIPANTS: Two hundred thirty-seven COVID-19 participants with a new-onset smell loss were recruited into the study. Two hundred twenty-two participants met the inclusion criteria and were randomised into three groups: corticosteroid irrigation, saline irrigation and no treatment. MAIN OUTCOME MEASURES: The primary outcome was the mean difference in the smell sensation score among the groups after treatment at 1, 2 and 6 weeks. The secondary outcomes measurements included (1) a self-rating quality of life (QOL)-related smell dysfunction score, (2) the change over time in smell sensation score and self-rating QOL-related smell dysfunction score and (3) the median time to complete recovery of smell loss. RESULTS: The mean differences in smell sensation scores among the three groups were not statistically significant at any follow-up period. The mean score of self-rating QOL-related smell dysfunction in the corticosteroid group was significantly better than the other groups at 1 week. The change of outcome scores showed significant improvement over time, regardless of the treatments. The median time to complete smell recovery was similar: 3 weeks. CONCLUSION: This study emphasised that corticosteroid nasal irrigation is not superior to saline or no nasal irrigation in restoring the sense of smell in COVID-19-associated olfactory loss.

Therapies for Olfactory Dysfunction - an Update.

PURPOSE OF REVIEW: Olfactory dysfunction is a prevalent condition affecting 5-15% of the general population, with significant impact on quality of life. This review summarizes the most recent and relevant literature in the treatment of olfactory dysfunction. RECENT FINDINGS: Current evidence supports the short-term use of topical corticosteroids and systemic therapy. These treatments may occur in conjunction with olfactory training, which is well supported by the literature. While there are several additional treatments currently under investigation, meaningful conclusions are not yet able to be made regarding their efficacy. The treatment of olfactory dysfunction is targeted at the suspected etiology when possible. After normal aging, chronic rhinosinusitis, post-infectious sequelae including as a result SARS-CoV-2 infection (COVID-19), and head trauma are the most common causes. Current evidence supports the short-term use of topical corticosteroids and systemic therapy. Several additional treatments are under investigation but recommendations for their use cannot currently be made.

Chemosensory loss in COVID-19.

The COVID-19 pandemic caused by SARS-CoV-2 virus quickly spread globally, infecting over half a billion individuals, and killing over 6 million*. One of the more unusual symptoms was patients' complaints of sudden loss of smell and/or taste, a symptom that has become more apparent as the virus mutated into different variants. Anosmia and ageusia, the loss of smell and taste, respectively, seem to be transient for some individuals, but for others persists even after recovery from the infection. Causes for COVID-19-associated chemosensory loss have undergone several hypotheses. These include non-functional or destroyed olfactory neurons and gustatory receptors or of their supporting cells, disruption of the signaling protein Neuropilin-1, and disruption in the interaction with semaphorins, key molecules in the gustatory and olfactory axon guidance. The current paper will review these hypotheses and chart out potential therapeutic avenues.

Recovery from Covid-19 smell loss: Two-years of follow up.

OBJECTIVE: To report long-term patterns of recovery and non-recovery in a large nationwide cohort of subjects with COVID-19 associated smell loss. STUDY DESIGN: Prospectively, longitudinal questionnaires. SETTING: Web-based national survey. METHODS: A longitudinal survey of adults with COVID-19 and/or sudden change in smell or taste since January 1, 2020 was launched April 10, 2020. Participants were queried again in late May 2022 regarding recovery. Data from respondents with >2 years since loss were analyzed and compared to recovery status of those more recently effected. RESULTS: 1103 responded to the survey of whom 946 met inclusion criteria. Among the 267 respondents for whom at least 2 years of follow up was available, 38.2 % reported full recovery, 54.3 % partial, and 7.5 % no recovery. For the entire cohort (all with ≥3 months since smell loss), 38.7 % reported complete recovery, 51.0 % reported partial recovery (ranging from mild complaints to severe phantosmia or dysosmia), and 10.3 % reported no improvement at all. Complete recovery of smell function was significantly higher in those under 40 years old (45.6 % compared to 32.9 % in those over 40). CONCLUSION: Although the vast majority of subjects who do recover do so within the first 3 months, long-term spontaneous recovery can occur. Rates of recovery do not seem to differ depending on when during the pandemic the loss first occurred.

Acupuncture is associated with a positive effect on odour discrimination in patients with postinfectious smell loss-a controlled prospective study.

INTRODUCTION: Smell disorders are common in the general population and occur e.g., after infections, trauma or idiopathically Treatment strategies for smell loss range from surgery, medication to olfactory training, depending on the pathology, but they are limited This study examined the effect of acupuncture on olfactory function. METHODS: Sixty patients with smell loss following infections of the upper respiratory tract were included in this investigation Half of the study group were randomly assigned to verum acupuncture and the other half to sham acupuncture Olfaction was measured by means of the "Sniffin' Sticks" test battery (odour threshold, discrimination and identification). RESULTS: Compared to sham acupuncture, verum was associated with an improvement of smell function as measured by the TDI score (p = 0.039) The improvement was largely determined by improvement in odour discrimination, and was significantly better in patients with a shorter duration of the disorder. CONCLUSION: The present results suggest that acupuncture is an effective supplementary treatment option for patients with olfactory loss.

[Diagnosis and Therapy of Olfactory Dysfunction - State of the ArtThe neglected sense-new evidence highlights the significance of the human sense of smell]. / Riechstörungen evidenzbasiert diagnostizieren und behandeln. Der unterschätzte Sinn ­ neue Erkenntnisse belegen die Bedeutung und Leistungsfähigkeit des menschlichen Geruchssinns.

Recent research shows that the human sense of smell seems to be more efficient than previously believed and to have a major impact on our health condition and quality of life. During the COVID-19 pandemic, an increased clinical interest has become evident for the SARS-CoV-2 related impact on olfactory function. This article highlights important aspects in the diagnosis and therapy of the chemical senses.

Viral infection and smell loss: The case of COVID-19.

Olfactory disorders have been increasingly reported in individuals infected with SARS-CoV-2, the virus causing the coronavirus disease 2019 (COVID-19). Losing the sense of smell has a strong impact on the quality of life, since it may lead to malnutrition, weight loss, food poisoning, depression, and exposure to dangerous chemicals. Individuals who suffer from anosmia (inability to smell) also cannot sense the flavor of food, which is a combination of taste and smell. Interestingly, infected individuals have reported sudden loss of smell with no congested nose, as is frequently observed in common colds or other upper respiratory tract infections. These observations suggest that SARS-CoV-2 infection leads to olfactory loss through a distinct mechanism, which is still unclear. This article provides an overview of olfactory loss and the recent findings relating to COVID-19. Possible mechanisms of SARS-CoV-2-induced olfactory loss are also discussed.

Structural and metabolic brain abnormalities in COVID-19 patients with sudden loss of smell.

OBJECTIVES: Sudden loss of smell is a very common symptom of coronavirus disease 19 (COVID-19). This study characterizes the structural and metabolic cerebral correlates of dysosmia in patients with COVID-19. METHODS: Structural brain magnetic resonance imaging (MRI) and positron emission tomography with [18F]-fluorodeoxyglucose (FDG-PET) were prospectively acquired simultaneously on a hybrid PET-MR in 12 patients (2 males, 10 females, mean age: 42.6 years, age range: 23-60 years) with sudden dysosmia and positive detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on nasopharyngeal swab specimens. FDG-PET data were analyzed using a voxel-based approach and compared with that of a group of healthy subjects. RESULTS: Bilateral blocking of the olfactory cleft was observed in six patients, while subtle olfactory bulb asymmetry was found in three patients. No MRI signal abnormality downstream of the olfactory tract was observed. Decrease or increase in glucose metabolism abnormalities was observed (p < .001 uncorrected, k ≥ 50 voxels) in core olfactory and high-order neocortical areas. A modulation of regional cerebral glucose metabolism by the severity and the duration of COVID-19-related dysosmia was disclosed using correlation analyses. CONCLUSIONS: This PET-MR study suggests that sudden loss of smell in COVID-19 is not related to central involvement due to SARS-CoV-2 neuroinvasiveness. Loss of smell is associated with subtle cerebral metabolic changes in core olfactory and high-order cortical areas likely related to combined processes of deafferentation and active functional reorganization secondary to the lack of olfactory stimulation.

SCENTinel 1.0: Development of a Rapid Test to Screen for Smell Loss.

Commercially available smell tests are primarily used in research or in-depth clinical evaluations and are too costly and time-consuming for population surveillance in health emergencies like COVID-19. To address this need, we developed the SCENTinel 1.0 test, which rapidly evaluates 3 olfactory functions: detection, intensity, and identification. We tested whether self-administering the SCENTinel 1.0 test discriminates between individuals with self-reported smell loss and those with average smell ability (normosmic individuals) and provides performance comparable to the validated and standardized NIH Toolbox Odor Identification Test in normosmic individuals. Using Bayesian linear models and prognostic classification algorithms, we compared the SCENTinel 1.0 performance of a group of self-reported anosmic individuals (N = 111, 47 ± 13 years old, F = 71%) and normosmic individuals (N = 154, 47 ± 14 years old, F = 74%) as well as individuals reporting other smell disorders (such as hyposmia or parosmia; N = 42, 55 ± 10 years old, F = 67%). Ninety-four percent of normosmic individuals met our SCENTinel 1.0 accuracy criteria compared with only 10% of anosmic individuals and 64% of individuals with other smell disorders. Overall performance on SCENTinel 1.0 predicted belonging to the normosmic group better than identification or detection alone (vs. anosmic: AUC = 0.95, specificity = 0.94). Odor intensity provided the best single-feature predictor to classify normosmic individuals. Among normosmic individuals, 92% met the accuracy criteria at both SCENTinel 1.0 and the NIH Toolbox Odor Identification Test. SCENTinel 1.0 is a practical test able to discriminate individuals with smell loss and will likely be useful in many clinical situations, including COVID-19 symptom screening.

Recovery From COVID-19-Related Olfactory Disorders and Quality of Life: Insights From an Observational Online Study.

Although olfactory disorders (OD) are among the most significant symptoms of COVID-19, recovery time from COVID-19-related OD and their consequences on the quality of life remain poorly documented. We investigated the characteristics and behavioral consequences of COVID-19-related OD using a large-scale study involving 3111 French respondents (78% women) to an online questionnaire over a period of 9 months covering different epidemic waves (from 8 April 2020 to 13 January 2021). In the patients who subjectively recovered from COVID-19-related OD (N = 609), recovery occurred on average after 16 days and most of the time within 1 month ("normal" recovery range); 49 subjectively recovered in 1-2.5 months, and several cases took up to 6.5 months. Among the patients with ongoing OD (N = 2502), 974 were outside the "normal" recovery range (persistent OD) and reported OD for 1-10 months. Developing a persistent OD was more likely with increasing age and in women and was more often associated with parosmia and phantosmia. The deleterious impact of COVID-19-related OD on the quality of life was significantly aggravated by OD duration and was more pronounced in women. Because persistent OD is not infrequent after COVID-19, has deleterious consequences on the quality of life, and receives few solutions from the health practitioners, it would be beneficial to implement screening and treatment programs to minimize the long-term behavioral consequences of COVID-19-related OD.

Serum vitamin D level is associated with smell dysfunction independently of aeroallergen sensitization, nasal obstruction, and the presence of allergic rhinitis in children.

BACKGROUND: Smell dysfunction is highly prevalent worldwide and has adverse effects on quality of life. Smell loss in rhinitis subjects is mainly caused by mechanical obstruction of odorant transmission due to mucosal type 2 inflammation. We determined the association of 25-hydroxyvitamin D (25[OH]D) levels with the severity of smell dysfunction in children. METHODS: We measured the olfactory threshold score in a total of 518 children (10-12 years old, 264 boys) using the Sniffin' Sticks kit, and the children were divided into tertiles according to olfactory threshold score. We also assessed serum 25[OH]D level, common aeroallergen-specific immunoglobulin E, rhinitis severity with visual analog scale, and the Total Four Symptom Score, and pre- and post-decongestant nasal patency with acoustic rhinometry. RESULTS: The children with 25(OH)D deficiency had significantly reduced mean olfactory threshold scores when compared to those with 25(OH)D levels of ≥20.0 ng/mL (6.56 ± 3.54 and 7.28 ± 3.87, respectively, P = .036). The proportion of loss of smell function and pre-decongestant nasal patency significantly associated with low 25(OH)D levels (chi-square trend test, P for trend = .007). Likewise, after adjustment for confounders, children with smell loss (third tertile) were significantly associated with low 25(OH)D level (aß=-0.062, 95% CI=-0.064 to -0.060, P = .009) independent of aeroallergen sensitization, and a low pre-decongestant nasal patency. CONCLUSIONS: 25-Hydroxyvitamin D is significantly associated with smell dysfunction independent of aeroallergen sensitization, nasal obstruction, and the presence of allergic rhinitis. This finding may provide insight into the mechanisms involved in the development of olfactory dysfunction.

Distorted chemosensory perception and female sex associate with persistent smell and/or taste loss in people with SARS-CoV-2 antibodies: a community based cohort study investigating clinical course and resolution of acute smell and/or taste loss in people with and without SARS-CoV-2 antibodies in London, UK.

BACKGROUND: Loss of smell and/or taste are cardinal symptoms of COVID-19. 'Long-COVID', persistence of symptoms, affects around one fifth of people. However, data regarding the clinical resolution of loss of smell and/or taste are lacking. In this study we assess smell and taste loss resolution at 4-6 week follow-up, aim to identify risk factors for persistent smell loss and describe smell loss as a feature of long-COVID in a community cohort in London with known SARS-CoV-2 IgG/IgM antibody status. We also compare subjective and objective smell assessments in a subset of participants. METHODS: Four hundred sixty-seven participants with acute loss of smell and/or taste who had undergone SARS-CoV-2 IgG/IgM antibody testing 4-6 weeks earlier completed a follow-up questionnaire about resolution of their symptoms. A subsample of 50 participants completed an objective olfactory test and results were compared to subjective smell evaluations. RESULTS: People with SARS-CoV-2 antibodies with an acute loss of sense of smell and taste were significantly less likely to recover their sense of smell/taste than people who were seronegative (smell recovery: 57.7% vs. 72.1%, p = 0.027. taste recovery 66.2% vs. 80.3%, p = 0.017). In SARS-CoV-2 positive participants, a higher percentage of male participants reported full resolution of smell loss (72.8% vs. 51.4%; p < 0.001) compared to female participants, who were almost 2.5-times more likely to have ongoing smell loss after 4-6 weeks (OR 2.46, 95%CI 1.47-4.13, p = 0.001). Female participants with SARS-CoV-2 antibodies and unresolved smell loss and unresolved taste loss were significantly older (> 40 years) than those who reported full resolution. Participants who experienced parosmia reported lower smell recovery rates and participants with distorted taste perception lower taste recovery rates. Parosmia had a significant association to unresolved smell loss (OR 2.47, 95%CI 1.54-4.00, p < 0.001). CONCLUSION: Although smell and/or taste loss are often transient manifestations of COVID-19, 42% of participants had ongoing loss of smell, 34% loss of taste and 36% loss of smell and taste at 4-6 weeks follow-up, which constitute symptoms of 'long-COVID'. Females (particularly > 40 years) and people with a distorted perception of their sense of smell/taste are likely to benefit from prioritised early therapeutic interventions. TRIALS REGISTRATION: ClinicalTrials.gov NCT04377815 Date of registration: 23/04/2020.

Objective gustatory and olfactory dysfunction in COVID-19 patients: a prospective cross-sectional study.

PURPOSE: To determine the prevalence of objective gustatory (GD) and olfactory (OD) dysfunction in COVID-19 patients. METHODS: This is a prospective, cross-sectional study of 51 COVID-19 positive patients diagnosed using RT-PCR-based testing. Of these study participants, 41 reported having present GD and OD at the time of enrollment and ten patients were without symptomatic OD and GD. All participants were objectively tested for OD by Brief Smell Identification Test (BSIT) and for GD by Burghart taste strip test, which were mailed to the participants. The subjective presence and severity of COVID-19 symptoms of smell loss, loss of taste, nasal obstruction, rhinorrhea/mucus production, fever, cough and shortness of breath were also assessed. RESULTS: Of the 41 patients with GD and OD, only 25.6% (10/39; p ≤ 0.0001) objectively presented GD and 39.1% (16/41; p ≤ 0.0001) OD at the time of their subjective dysfunction. Regarding GD, 23.1% (9/39) suffered from total hypogeusia, 2.6% (1/39) from ageusia. A significant loss of sour (33.3% (13/39)) and salty taste (17.9% (7/39)) could be recognized. Only 10.3% (4/39) showed a reduction in sweet and bitter taste. Concerning OD, 9.8% (4/41) showed a deficit relative to younger age in the BSIT and 29.3% (12/41) results abnormal relative to age. CONCLUSION: Subjective and objective findings in GD and OD differ significantly. Most patients suffering from objective dysgeusia present a deficit in sour and salty taste. TRIAL REGISTRATION NUMBER: DRKS00021516; 22/04/2020.

Symptomatology of COVID-19 from the otorhinolaryngology perspective: a survey of 223 SARS-CoV-2 RNA-positive patients.

PURPOSE: To determine prevalence, severity, duration, and time from onset to diagnosis of general and Otorhinolaryngologic symptoms related to COVID-19 in whole disease spectrum: from mild to critical patients. METHODS: All adult patients with positive SARS-CoV-2 RNA found in nasopharyngeal and oropharyngeal swabs between March 10 and April 21, 2020 were surveyed by the authors for new onset symptoms during disease course. Demographic features, general symptoms, and Otorhinolaryngological symptoms were evaluated and compared by disease severity. RESULTS: Of 223 included patients, 18.4% had mild, 61.4%; moderate, 14.3%; severe, and 5.8%; critical disease. Median age was 51 (range 20-93), 113 (50.7%) were male and 110 (49.3%) were female. The most common general symptoms were fatigue, cough, and fever with respective frequencies of 71.3%, 54.3%, and 50.7%. The most common Otorhinolaryngologic symptoms were taste loss, smell loss, and sore throat with respective frequencies of 34.5%, 31.8%, and 26%. Fatigue, fever, and dyspnea were more common in severe-critical patients compared to mild-moderate patients (p = 0.029, p = 0.016, and p < 0.001, respectively). Only smell loss was more common in mild-moderate group (p = 0.003). Prevalence of other symptoms did not differ between groups. Symptom durations and onset time to diagnosis varied. CONCLUSION: When compared to the previous studies, while general symptoms were less common, Otorhinolaryngologic symptoms were more common in our study population. Considering high infection risks, Otorhinolaryngologists should be aware of COVID-19 patients presenting with Otorhinolaryngologic complaints.

Etiologies of olfactory dysfunction in a pediatric population: based on a retrospective analysis of data from an outpatient clinic.

PURPOSE: Although the prevalence of olfactory dysfunction in children is thought to be lower compared to adults, little is known about the actual frequency of etiologies of smell dysfunction in children. Aim of the study was (i) to describe the epidemiology of olfactory dysfunction in a pediatric population and (ii) to compare the distribution of etiologies to adults. MATERIAL AND METHODS: Data of patients consulting a smell and taste clinic between 2000 and 2017 were retrospectively analyzed. Frequency of major causes of olfactory dysfunction was examined with a focus on the pediatric population. RESULTS: A total of 7153 patients (164 children) were included in the analysis. Most children presented with congenital olfactory dysfunction (67%), or head-trauma (12%). In contrast, the cumulative frequency of olfactory loss associated with sinonasal disorders or acute infections of the upper airways was 6%. The frequency of etiologies of olfactory dysfunction changed with age: While the frequency of patients with congenital anosmia decreased, the frequency of causes related to infections of the upper respiratory tract and idiopathic causes increased. CONCLUSION: About 2/3 of olfactory dysfunction in children are congenital while 1/3 is acquired. The frequency of etiologies causing olfactory dysfunction change significantly from children to an adult population.