Olfactory Symptoms Research Articles

Are olfactory and gustatory symptoms useful at predicting disease severity markers in COVID-19 infection?

The relationship between olfactory and gustatory dysfunction (OGD) and COVID-19 infection severity is still unclear. To investigate the correlation between OGD in COVID-19-infected individuals and RT-PCR results, chest CT scan abnormality, lymphocyte counts, hospital admission units, age, body temperature, and blood oxygen saturation. Case-control study. The sample was composed of laboratory and chest X-ray confirmed COVID-19-infected patients from four hospitals. The patients were divided into case and control groups based on the presence of OGD symptoms. The predictor variable was OGD. The outcome variable was gender, hospital admission unit, chest CT scan abnormality, PCR, lymphocyte counts, age, body temperature, and blood oxygen saturation. Bivariate statistics were computed and the P value was set at 0.05. The sample consisted of 189 patients. Smell and taste disorders were found in 31.7% and 24.3% of patients, respectively. OGD was significantly correlated with positive PCR results (P < 0.001) and general unit admission (P < 0.05) during hospitalization. Additionally, patients with OGD had significantly lower mean age (P < 0.001), higher body temperature (P < 0.01), and blood oxygen saturation (P < 0.01). However, OGD was not correlated with gender, chest CT scan abnormality, or lymphocyte counts (P > 0.05). OGD symptoms can be used to detect COVID-19-infected patients. OGD can be used to predict less severe disease mainly by its correlation with the less amount of hospital care, more negative PCR results, higher body temperature, and higher blood oxygen saturation.

好酸球性副鼻腔炎手術症例における嗅覚障害自覚症状の変化

好酸球性副鼻腔炎手術症例における嗅覚障害自覚症状の変化

Novel PAX6 variant in a family with ophthalmologic, pancreatic, and olfactory features.

Variants in the PAX6 gene have been associated with ophthalmologic, neurologic, and pancreatic differences. We report on a proband, mother, and affected brother who presented with congenital cataracts and glaucoma at a young age. Nonocular findings are also reported among these family members. After a congenital cataracts next-generation sequencing (NGS) gene panel was found to be nondiagnostic in 2016, a more expanded panel in 2020 revealed a novel variant: c.178T > A; p.Tyr60Asn in exon 6 of the PAX6 gene in the proband. The variant is also present in the affected mother and affected brother; it is absent in an unaffected brother. The clinical findings of these three relatives, in conjunction with their genetic testing and the associated PAX6 features reported in the literature, suggest that this novel familial variant may be an underlying etiology for these individuals’ ophthalmologic, pancreatic, and olfactory symptoms.

Prevalence of Olfactory Dysfuntion in SARS-COV-2 Positive Patients.

Severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) is associated with chemosensory symptoms including olfactory dysfunction and dysgeusia. Multiple studies have reported differing prevalence rates of symptoms and recovery rates depending on geographic location. The purpose of the study was to determine the prevalence and features of Covid19 olfactory dysfunction in a developing nation. We conducted a prospective study at a tertiary, high-volume centre in South Africa, to determine the prevalence of olfactory dysfunction in SARS-COV-2 positive patients. The average recovery time of the olfactory dysfunction was also evaluated. The study included patients diagnosed with SARS-COV-2 infection between November 2020 and January 2021. Patients were recruited to participate in a survey which assessed demographic data, date of diagnosis, initial symptoms, presence and recovery time of olfactory dysfunction symptoms. A total of 86 patients with olfactory dysfunction were included and followed up telephonically over 6 weeks in 2 week intervals to determine recovery time. There was a prevalence rate of 40.7% of olfactory dysfunction in patients in our study. A higher proportion of patients with olfactory dysfunction had fever compared to those without and this was a significant finding in our study population. The overall median recovery time in our study was 7 days. Prevalence of olfactory dysfunction in our population is in keeping with European studies and most patients recover their sense of smell within a week.

Machine Learning Refutes Loss of Smell as a Risk Indicator of Diabetes Mellitus.

Because it is associated with central nervous changes, and olfactory dysfunction has been reported with increased prevalence among persons with diabetes, this study addressed the question of whether the risk of developing diabetes in the next 10 years is reflected in olfactory symptoms. In a cross-sectional study, in 164 individuals seeking medical consulting for possible diabetes, olfactory function was evaluated using a standardized clinical test assessing olfactory threshold, odor discrimination, and odor identification. Metabolomics parameters were assessed via blood concentrations. The individual diabetes risk was quantified according to the validated German version of the “FINDRISK” diabetes risk score. Machine learning algorithms trained with metabolomics patterns predicted low or high diabetes risk with a balanced accuracy of 63–75%. Similarly, olfactory subtest results predicted the olfactory dysfunction category with a balanced accuracy of 85–94%, occasionally reaching 100%. However, olfactory subtest results failed to improve the prediction of diabetes risk based on metabolomics data, and metabolomics data did not improve the prediction of the olfactory dysfunction category based on olfactory subtest results. Results of the present study suggest that olfactory function is not a useful predictor of diabetes.

Gustatory and olfactory dysfunctions in hospitalised patients with COVID-19 pneumonia: a prospective study

ImportanceIdentifying undetected clinical signs is imperative in the prevention of SARS-CoV-2.ObjectiveTo establish the prevalence of clinical gustatory and olfactory dysfunctions in patients with COVID-19 pneumonia. Clinical outcomes and recovery rates...

Olfactory and Gustatory Dysfunctions in Patients With Laboratory-Confirmed COVID-19 Infection: A Change in the Trend

To study the presence of olfactory and gustatory dysfunctions in patients with laboratory-confirmed COVID-19 infection in our set up. Longitudinal study, 1st March 2020-15th August 2020, at a tertiary care hospital. RT PCR positive for SARSCoV-2 patients, above 18 years age included. Excluding patients with previous history of changes in smell or taste sensation, severely ill at the time of admission, history of taking drugs at the time of COVID 19 infection that affect the smell or taste sensation. 435 patients included after obtaining an institutional ethical clearance. After an informed consent, these patients were followed up telephonically, to record any subjective improvement in olfactory or gustatory symptoms and an approximate duration of recovery. Olfactory and/or gustatory dysfunction 10.8% (47/435). Mean (SD) age—34.53(10.8) years. Females affected significantly more [X2 (1, N = 435) = 7.45, p value is 0.006, significant at p < 0.05]. Olfactory dysfunction significantly associated with gustatory dysfunction [X2 (1, n = 435) = 182.29, p < 0.00001]. 19.8% (N = 435) of individuals remained asymptomatic. Nasal symptoms rare (4%, N = 47). Mean (SD) recovery olfactory and gustatory dysfunction 12.1 (7.7) and10.8 (6.3) days respectively. Subjective loss of smell or taste dysfunction was far less common. Women and younger population reported olfactory or gustatory dysfunction commonly. Olfactory and gustatory changes without nasal symptoms, suspicion of COVID-19 infection is relevant. Recovery is complete and early.

Dl-3-n-Butylphthalide Alleviates Behavioral and Cognitive Symptoms Via Modulating Mitochondrial Dynamics in the A53T-α-Synuclein Mouse Model of Parkinson's Disease.

BackgroundAggregation and neurotoxicity of the presynaptic protein α-synuclein and the progressive loss of nigral dopaminergic neurons are believed to be the key hallmarks of Parkinson’s disease (PD). A53T mutant α-synuclein causes early onset PD and more severe manifestations. A growing body of evidence shows that misfolding or deposition of α-synuclein is linked to the maintenance of mitochondrial dynamics, which has been proven to play an important role in the pathogenesis of PD. It has been observed that Dl-3-n-butylphthalide (NBP) may be safe and effective in improving the non-tremor-dominant PD. However, the potential mechanism remains unclear. This study aimed to investigate whether NBP could decrease the loss of dopaminergic neurons and α-synuclein deposition and explore its possible neuroprotective mechanisms.MethodsA total of 20 twelve-month-old human A53T α-synuclein transgenic mice and 10 matched adult C57BL/6 mice were included in the study; 10 adult C57BL/6 mice were selected as the control group and administered with saline (0.2 ml daily for 14 days); 20 human A53T α-synuclein transgenic mice were randomly divided into A53T group (treated in the same manner as in the control group) and A53T + NBP group (treated with NBP 0.2 ml daily for 14 days). Several markers of mitochondrial fission and fusion and mitophagy were determined, and the behavioral, olfactory, and cognitive symptoms were assessed as well.ResultsIn the present study, it was observed that the A53T-α-synuclein PD mice exhibited anxiety-like behavioral disturbance, impairment of coordination ability, memory deficits, and olfactory dysfunction, loss of dopaminergic neurons, and α-synuclein accumulation. Meanwhile, the mitofusin 1 expression was significantly decreased, and the mitochondrial number and dynamin-related protein 1, Parkin, and LC3 levels were increased. The detected levels of all markers were reversed by NBP treatment, and the mitochondrial morphology was partially recovered.ConclusionIn the present study, a valuable neuropharmacological role of NBP has been established in the A53T-α-synuclein PD mouse model. Possible neuroprotective mechanisms might be that NBP is involved in the maintenance of mitochondrial dynamics including mitochondrial fission and fusion and clearance of damaged mitochondria. It is essential to perform further experiments to shed light on the precise mechanisms of NBP on mitochondrial homeostasis.

Persistent olfactory complaints after COVID-19: a new interpretation of the psychophysical olfactory scores

Background: Sudden olfactory loss is a major symptom of SARS-CoV-2 infection and has a negative impact on daily life quality. Almost 80% of disorders regress spontaneously. No precise characterization of the medium- and long-term olfactory symptoms has been carried out yet, apart from self-assessments. The main objective of this work was to characterize persistent smell disorders in this population. Methodology: Consecutive patients consulting to the ENT department with post-Covid19 olfactory loss were included. The clinical examination included an analog scale for the self-assessment of olfactory recovery), a nasofibroscopy, the Sniffin’ Stick Test and the short version of the Questionnaire of olfactory disorders. Results: Among the 34 patients included, based on the Sniffin’ Sticks Test, 29.4% (n=10) could be classified as normosmic, 55.9% (n=19) as hyposmic and 14.7% (n=5) as functional anosmic). Only olfactory identification impairment was significantly correlated with olfactory complaint and daily anxiety and annoyance related to lack of olfaction recovery. This identification disorder seemed to worsen over time. Conclusions: It is crucial to assess odor identification disorders in case of persistent olfactory complaints after COVID-19. It is fundamental to target this disorder, as it does not improve spontaneously and negatively impact quality of life.

Olfactory Dysfunction in Frontline Health Care Professionals During COVID-19 Pandemic in Brazil.

Upper respiratory viral infections can decrease the sense of smell either by inflammatory restriction of nasal airflow that carries the odorant molecules or through interference in olfactory sensory neuron function. During the coronavirus disease 2019 (COVID-19) pandemic, triggered by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), worldwide reports of severe smell loss (anosmia/hyposmia) revealed a different type of olfactory dysfunction associated with respiratory virus infection. Since self-reported perception of smell is subjective and SARS-CoV-2 exposure is variable in the general population, we aimed to study a population that would be more homogeneously exposed to the virus. Here, we investigated the prevalence of olfactory loss in frontline health professionals diagnosed with COVID-19 in Brazil, one of the major epicenters of the disease. We also analyzed the rate of olfactory function recovery and the particular characteristics of olfactory deficit in this population. A widely disclosed cross-sectional online survey directed to health care workers was developed by a group of researchers to collect data concerning demographic information, general symptoms, otolaryngological symptoms, comorbidities, and COVID-19 test results. Of the 1,376 health professionals who completed the questionnaire, 795 (57.8%) were working directly with COVID-19 patients, either in intensive care units, emergency rooms, wards, outpatient clinics, or other areas. Five-hundred forty-one (39.3%) participants tested positive for SARS-CoV-2, and 509 (37%) were not tested. Prevalence of olfactory dysfunction in COVID-19-positive subjects was 83.9% (454 of 541) compared to 12.9% (42 of 326) of those who tested negative and to 14.9% (76 of 509) of those not tested. Olfactory dysfunction incidence was higher in those working in wards, emergency rooms, and intensive care units compared to professionals in outpatient clinics. In general, remission from olfactory symptoms was frequent by the time of responses. Taste disturbances were present in 74.1% of infected participants and were significantly associated with hyposmia. In conclusion, olfactory dysfunction is highly correlated with exposure to SARS-CoV-2 in health care professionals, and remission rates up to 2 weeks are high.

Spectrum of Non-Motor Symptoms in Parkinson's Disease.

Parkinson's disease is predominantly classified as a movement disorder. Beyond the textbook definition of rigidity, tremors, and bradykinesia, Parkinson's disease encompasses an entire entity of non-motor symptom complexes that can precede the motor features by many years. Despite their significant clinical importance, the awareness of non-motor symptoms is quite negligible. Sleep disorders, gastrointestinal dysfunction, olfactory disturbances, anxiety, and depressive episodes are some of the most common non-motor presentations. The wide-spread occurrence of olfactory symptoms and the low cost of the assessment, is favoring olfactory dysfunction as a potential biomarker in Parkinson's. Sleep disorders may manifest before the motor and autonomic symptoms and might be linked to concomitant sleeping disorders like insomnia, REM sleep disorders, restless leg syndrome, narcolepsy, or obstructive sleep apnea. Non-motor symptoms can deteriorate the quality of life in Parkinson’s patients. Early detection of non-motor symptoms can help in the diagnosis of Parkinson’s disease and can fairly improve the survival and prognosis of these patients.

Chemosensory Systems in COVID-19: Evolution of Scientific Research.

COVID-19 disease induced by coronavirus SARS-CoV-2 presents among its symptoms alterations of the chemosensory functions. In the first studies on the Chinese population, this symptomatology was not particularly relevant, and hyposmia and hypogeusia were excluded from the symptoms to be evaluated to diagnose the disease. With the pandemic spread of the illness, there has been an augment in reports on chemosensory dysfunctions among patients. The first data analysis showed the presence of these disorders mainly in paucisymptomatic and asymptomatic patients. The interest in chemosensory systems therefore increased considerably, because the olfactory and gustatory symptoms could be the key to stop the infection spread. Furthermore, the degree of alert and attention grew, considering that these types of dysfunctions are prognostic symptoms of serious neurodegenerative diseases. About 9 months have passed since the first anecdotal reports on the involvement of the olfactory and gustatory systems in the COVID-19 pathology. For this reason, a careful review of the literature was conducted to understand if it is clearer which people present chemosensory symptoms and if these are related to the severity of the disease. Furthermore, we have identified which aspects still remain to be clarified.

Predictive Value of Olfactory and Taste Symptoms in the Diagnosis of COVID-19: A Systematic Review and Meta-Analysis.

ObjectivesThis study evaluated the diagnostic value of various symptoms of coronavirus disease 2019 (COVID-19) in screening for this disease.MethodsTwo authors (working independently) comprehensively reviewed six databases (PubMed, Cochrane Database, Embase, Web of Science, Scopus, and Google Scholar) from their dates of inception until November 2020. The predictive value of patient-reported symptoms, including otolaryngologic and general symptoms, was evaluated in adults who underwent testing for COVID-19. True-positive, true-negative, false-positive, and false-negative data were extracted from each study. The methodological quality of the included studies was evaluated using the quality assessment of diagnostic accuracy studies tool (ver. 2).ResultsTwenty-eight prospective and retrospective studies were included in the meta-analysis. The diagnostic odds ratio (DOR) of a change in olfaction and/or taste was 10.20 (95% confidence interval [CI], 8.43–12.34). The area under the summary receiver operating characteristic curve was 0.8. Olfactory and/or taste changes had a low sensitivity (0.57; 95% CI, 0.47–0.66) but moderate negative (0.78; 95% CI, 0.69–0.85] and positive (0.78; 95% CI, 0.66–0.87) predictive values and a high specificity (0.91; 95% CI, 0.83–0.96). Olfactory and/or taste changes had a higher diagnostic value than the other otolaryngologic symptoms, a higher DOR and specificity, and a similar or higher diagnostic value than the other general symptoms.ConclusionAmong otolaryngologic symptoms, olfactory and/or taste dysfunction was the most closely associated with COVID-19 and its general symptoms, and should therefore be considered when screening for the disease.

Intranasal treatment of lixisenatide attenuated emotional and olfactory symptoms via CREB-mediated adult neurogenesis in mouse depression model.

Convergent lines of evidence indicate a striking correlation between olfactory deficits and depressive symptoms. However, the effectiveness of intranasal treatment of antidepressant or other neurotrophic agents remains poorly understanding. Here in this study, we created depression mouse model and explored the antidepressant effects of GLP-1 analog lixisenatide (LXT) with intranasal treatment. Consecutive intranasal treatment of LXT remarkably reduced the depressive and anxiety behaviors. Meanwhile, it also improved the olfactory memory and olfactory sensitivity. Immunofluorescent analysis demonstrated the LXT improved the adult neurogenesis in olfactory system and hippocampus. Inhibition of adult neurogenesis with TMZ caused the compromised effects of LXT in improving emotional and olfactory functions, suggesting the vital role of adult neurogenesis in LXT induced depression therapeutic effects. Treatment of LXT resulted in the increased phosphorylation of CREB protein in hippocampal tissue, indicating CREB plays important roles in antidepressant effects of LXT intranasal treatment. Inhibiting CREB with chemical approach decreased effects of LXT in reserving depression induced emotional and olfactory functions. In conclusion, our study suggests intranasal treatment of LXT could be a potential antidepressant to improve the olfactory functions as well as the emotional behaviors.

Olfactory Disturbances as Presenting Manifestation Among Egyptian Patients with COVID-19: Possible Role of Zinc.

COVID-19 is a severe acute respiratory syndrome caused by coronavirus 2 (SARS-CoV-2). Deficiency of zinc has been supposed to contribute to loss of smell and taste in COVID-19 patients. Our study aimed to assess the serum zinc levels among patients with COVID-19 of various severities, with and without olfaction dysfunction, and to evaluate the effect of zinc therapy in recovery of smell dysfunction among such patients. This study included 134 patients; real-time reverse transcription-polymerase chain reaction (rRT-PCR) proved SARS-CoV-2. Serum zinc levels were measured for all infected patients. One hundred and five patients were detected to have anosmia and/or hyposmia and were categorized randomly into 2 groups; the first group included 49 patients who received zinc therapy and the second group included 56 patients who did not received zinc. All patients were followed up for the recovery duration of olfactory and gustatory symptoms and duration of complete recovery of COVID-19. Olfactory dysfunction was reported in 105 patients (78.4%). Serum zinc levels were not significantly different between the patient subgroups regarding disease severity or the presence or absence of olfactory and/or gustatory dysfunction (p ˃ 0.05). The median duration of recovery of gustatory and/or olfactory function was significantly shorter among patients who received zinc therapy than those who did not received zinc (p < 0.001), while the median duration of complete recovery from COVID-19 was not significantly different among the two groups (p ˃ 0.05). Although the zinc status of COVID-19 patients did not exhibit a significant role in development of anosmia and/or hyposmia or disease severity, zinc therapy may have a significant role in shortening the duration of smell recovery in those patients without affecting the total recovery duration from COVID-19.

Smell dysfunction in patients with COVID-19

Coronavirus disease 2019 (COVID-19) is the cause of a global pandemic and the object of numerous studies worldwide. COVID-19 has many clinical manifestations, but smell dysfunction has become its unique “visiting card”. The purpose of this review is to analyze scientific data on anosmia in COVID-19 based on the results of primary research using PubMed, Google Scholar, and eLIBRARY databases. Olfactory dysfunction is a very common symptom in COVID-19: up to 85% of patients report these subjective sensations, but objective olfactory testing shows a higher prevalence — up to 98%. Up to 27% of patients may experience a sudden onset of anosmia as the first symptom. Therefore, anosmia can be crucial in timely identification of individuals infected with SARS-CoV 2. A feature of olfactory disorders in COVID-19 is the preservation of normal transnasal air flow conditions, when edema, hyperemia of the nasal mucosa and rhinorrhea characteristic of other respiratory viral infections are expressed slightly or aren`t expressed at all. Many studies show that the olfactory epithelium of the nasal cavity is an area of enhanced binding, replication, and accumulation of SARS-CoV2, which is due to the active expression of two host receptors (APF2 and TMPS2 proteases) by numerous non-neuronal olfactory epithelium cells. It is supposed that supporting cells of the olfactory epithelium are primarily affected, and olfactory receptor neurons and olfactory bulb neurons are affected secondarily. However, the final clinical and pathophysiological significance of olfactory symptoms remains to be determined

Olfactory and Gustatory Symptoms of Coronavirus Disease 2019: A Systematic Review and Meta-analysis

Introduction: There is increasing anecdotal evidence that olfactory and gustatory dysfunction may be associated with Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). Aim: The aim of this systematic review and meta-analysis was to find the association of olfactory and gustatory symptoms with Coronavirus Disease-19 (COVID-19) and estimate their pooled prevalence. Materials and Methods: PubMed, Embase, EBSCO and Cochrane databases were searched for cross-sectional, cohort and case-control studies evaluating olfactory and gustatory symptoms in patients with COVID-19. The search terms included COVID-19, severe acute respiratory syndrome coronavirus-2, coronavirus, olfaction disorders, anosmia, hyposmia, dysgeusia and ageusia. Random effects model was used to calculate a pooled Odds Ratio (OR) and pooled prevalence. Results: Total 14 studies were included in qualitative synthesis and 13 studies were incorporated in quantitative synthesis, involving 3,125 patients. The pooled OR was 15.59 reflecting that smell and taste disorders were strongly associated with COVID-19. The pooled prevalence of olfactory and gustatory dysfunction was 56% and 44%, respectively. Conclusion: It can be concluded that there is a significant association between olfactory and gustatory symptoms and COVID-19. Majority of the studies support the use of these symptoms as screening tools for COVID-19.

Prevalence and correlates of parosmia and phantosmia among smell disorders.

Among those many individuals who experience a reduced odor sensitivity (hyposmia/anosmia), some individuals also have disorders that lead to odor distortion, such as parosmia (i.e. distorted odor with a known source), or odor phantoms (i.e. odor sensation without an odor source). We surveyed a large population with at least one olfactory disorder (N = 2031) and found that odor distortions were common (46%), with respondents reporting either parosmia (19%), phantosmia (11%), or both (16%). In comparison to respondents with hyposmia or anosmia, respondents with parosmia were more likely to be female, young, and suffering from post-viral olfactory loss (P < 0.001), while respondents with phantosmia were more likely to be middle-aged (P < 0.01) and experiencing symptoms caused by head trauma (P < 0.01). In addition, parosmia, compared to phantosmia or anosmia/hyposmia, was most prevalent 3 months to a year after olfactory symptom onset (P < 0.001), which coincides with the timeline of physiological recovery. Finally, we observed that the frequency and duration of distortions negatively affects the quality of life, with parosmia showing a higher range of severity than phantosmia (P < 0.001). Previous research often grouped these distortions together, but our results show that they have distinct patterns of demographics, medical history, and loss in quality of life.

SELF-REPORTED SUDDEN ONSET HYPOSMIA: AN EARLY PRESENTATION OF SARS COV-2 INFECTION

The present outbreak of COVID-19 started in December 2019 in Wuhan, a city in Hubei province in China. The World health organization labeled the disease a global pandemic on March 11, 2020. The disease is caused by a virus called severe acute respiratory coronavirus-2 (SARS CoV-2). The individuals may remain asymptomatic or present with symptoms of infection. The common presenting symptoms include but are not limited to fever, dry or productive cough, malaise. Contrary to the typical clinical presentation of COVID-19, the patients may present with non-specific symptoms of olfactory or gustatory origin. The olfactory symptoms include hyposmia or anosmia. Physicians may be vigilant to screen and isolate patients with sudden onset hyposmia or anosmia, an early indication of infection that will minimize person-to-person transmission and will contain the virus spread. Keywords: COVID-19, SARS CoV-2, Hyposmia, Anosmia, Physician.

The temporal course of COVID-19 anosmia and relation to other clinical symptoms.

ObjectiveThis study aimed to define the clinical course of anosmia in relation to other clinical symptoms. Methods135 patients with COVID-19 were reached by phone and subsequently included in the study. Olfactory functions were evaluated using a questionnaire for assessment of self-reported olfactory function. Patients were divided into four subgroups according to the presence of olfactory symptoms and temporal relationship with the other symptoms: group1 had only olfactory complaints (isolated, sudden-onset loss of smell); group2 had sudden-onset loss of smell, followed by COVID-19 related complaints; group3 initially had COVID-19 related complaints, then gradually developed olfactory complaints; and group4 had no olfactory complaints.ResultsIn total, 59.3% of the patients interviewed had olfactory complaints during the disease course. The olfactory dysfunction severity during COVID-19 infection was significantly higher in group1 compared to groups 2 and 3. In groups1–3, the odor scores after recovery from COVID-19 disease were significantly lower compared to the status prior to disease onset. The residual olfactory dysfunction was similar between groups1 and 2, but was more evident than group3. Mean duration for loss of smell was 7.8 ± 3.1 (2–15) days. Duration of loss of smell was longer in groups1 and 2 than in group3. Odor scores completely returned back to the pre-disease values in 41 (51.2%) patients with olfactory dysfunction. Rate of complete olfactory dysfunction recovery was higher in group3 compared to groups1 and 2.ConclusionIn isolated anosmia cases, anosmia is more severe, and complete recovery rates are lower compared to the patients who have other clinical symptoms.Level of evidenceLevel 4.