Development of a Korean Culture-Friendly Olfactory Function Test and Optimization of a Diagnostic Cutoff Value

A tool for the psychophysical assessment of olfactory dysfunction in patients with COVID-19

Numerous studies have reported that patients with coronavirus disease 2019 (COVID-19) experience alterations in the sense of smell. Therefore, there is an increased need for a psychophysical evaluation tool for olfactory dysfunction in patients with COVID-19 without increasing the risk of virus spread. We applied a single-use sniffing-bead system, which consisted of small beads and a disposable plastic handpiece, to patients with COVID-19 presenting with olfactory dysfunction. The bead sets contained eight concentrations of 2-phenylethyl alcohol (PEA), which has been used in olfactory function tests for many years, and the lowest concentration at which the participant detected the PEA odor was recorded as the PEA threshold. The test was easily administered at the clinic during the consultation with the doctor without increasing the risk of virus spread. Based on the test results, anosmia was objectively confirmed in a patient with subjective anosmia, and another patient with subjective hyposmia was diagnosed with normosmia. Both patients started olfactory training after diagnosis. In conclusion, we present a system to psychophysically assess olfactory dysfunction in patients with COVID-19 using a universal odorant without the risk of virus spread, and suggest that this system might enable early diagnosis and management of patients with COVID-19.

Impact of Aeroallergen Sensitization on Chronic Rhinosinusitis

PURPOSE

This study investigated the impact of aeroallergens on the development and progression of chronic rhinosinusitis (CRS), with a focus on the specific associations between aeroallergens and CRS according to allergen type, number, and extent of sensitization.

METHODS

The medical records of 256 CRS patients were retrospectively analyzed. All were divided into nonallergic, house dust mite (HDM)-allergic, pollen-allergic, and double allergic groups via specific immunoglobulin E (IgE) testing. Clinical characteristics, computed tomography (CT) scores, olfactory functions, and demographic data were compared. Correlation analysis was performed to explore the relationships between the extent of allergen sensitization and CRS severity. Binary logistic regression analysis was used to identify risk factors for hyposmia and anosmia.

RESULTS

The allergic group exhibited higher total CT scores than the nonallergic group (P = 0.001). Sensitivity to HDM or pollen allergens alone was not significantly associated with increased CRS severity. No significant differences were observed between the effects of HDM and pollen allergens on CRS severity. However, the double allergic group exhibited significantly higher CT scores (P < 0.001, < 0.001, and 0.003) than the other groups. Although the prevalence rates of anosmia and hyposmia were notably higher in the double allergic group, the difference was not statistically significant. The maximum specific IgE levels to HDM and pollen allergens positively correlated with the CT scores (P = 0.001 and 0.001, respectively).

CONCLUSIONS

Allergen sensitization, particularly to multiple common allergens, contributed to CRS severity. CRS patients sensitized to both HDM and pollen allergens tended to experience the diminished olfactory function. These findings underscore the importance of considering the allergen sensitization pattern when assessing CRS severity and its potential progression.

Factors associated with impaired psychophysical gustatory function

OBJECTIVE

To investigate the clinical characteristics associated with measured gustatory dysfunction in patients with chemosensory (smell and taste) discomfort.

STUDY DESIGN

Retrospective study.

DESIGN

Hospital-based cohort.

SETTING

The clinical characteristics associated with the measured diagnosis of gustatory dysfunction were statistically analysed.

PARTICIPANTS

Patients who underwent all the psychophysical olfactory and chemical gustatory function tests (YSK olfactory function test and chemical gustometry exam) and the subjective questionnaires between October 2021 and February 2023.

MAIN OUTCOME MEASURES

YSK olfactory function test and chemical gustometry results, subjective questionnaire score about chemosensory (smell and taste) functions. The Medical records of patients who visited the smell and taste centre in a tertiary.

RESULTS

A total of 219 patients were enrolled; 180 were diagnosed as having normal gustatory function, and 39 were diagnosed as having gustatory dysfunction. Subjective recognition of gustatory function was not associated with the measured gustatory function. Age, sex, measured olfactory function and the threshold and discrimination scores for the olfactory function test were significant factors in the multivariate analysis. When the patients were further divided according to age, the threshold test scores rather than other subsets in the olfactory function test were significantly associated with measured gustatory dysfunction in patients 60 and older.

CONCLUSION

In older adult male patients with olfactory dysfunction, gustatory function should be considered regardless of subjective gustatory dysfunction.

Clinical characteristics of local allergic rhinitis sensitized to house dust mites in Asia

PURPOSE

Local allergic rhinitis (LAR) is characterized by a localized nasal allergic response without evidence of systemic atopy. LAR is an underdiagnosed entity and is a diagnostic and therapeutic challenge for clinicians. This study aimed to investigate the prevalence and clinical characteristics of patients with LAR to house dust mites (LAR-HDM) in Korea.

METHODS

We performed a retrospective chart review of 336 adult patients with rhinitis symptoms who visited the Rhinologic Clinic at Korea University Guro Hospital from October 2019 to April 2021. Using results of the skin prick test, serologic test, and nasal provocation test, patients were classified as allergic rhinitis (AR) to HDM (AR-HDM), AR to other allergens, non-allergic rhinitis (NAR), or LAR-HDM. We excluded patients with AR to other allergens and compared the clinical characteristics of the remaining three groups. Patient demographic data were reviewed, and patients' nasal symptoms, olfactory function, serum total IgE, and severity of accompanying rhinosinusitis were evaluated.

RESULTS

In total, 336 patients were examined. AR-HDM was diagnosed in 138 (41.1%) patients, AR to other allergens in 36 (10.7%) patients, NAR in 21 (42.0%) patients, and LAR-HDM in 21 (6.3%) patients. The mean age of patients with LAR-HDM was significantly higher than that of patients with AR-HDM. There were no significant differences in sex, smoking history, asthma, and family history of allergic diseases between the groups. Compared to NAR patients, there were significantly more patients with LAR-HDM who had persistent nasal symptoms. The frequency of nasal itching and sneezing was significantly higher in the LAR-HDM group than in the NAR group. The olfactory function score in the LAR-HDM group was significantly worse than that in the AR-HDM group, and the Lund-Mackay score was significantly higher in the LAR-HDM group than in the other groups.

CONCLUSION

Clinical history and nasal symptoms are very similar in LAR-HDM and AR-HDM. Clinicians should take more care to differentiate them. LAR-HDM should also be considered in patients with persistent and severe nasal symptoms without systemic atopy.

Validation of Korean Olfactory Questionnaire for Perioperative Olfactory Assessment in Endoscopic Endonasal Skull Base Surgery

Objective: To analyze changes in olfactory function after endoscopic endonasal skull base surgery and compare performance of the olfactory questionnaire with those of conventional psychophysical tests. Methods: Patients were classified into 5 categories for olfactory function evaluation (normal, mild hyposmia, moderate hyposmia, severe hyposmia, and anosmia) based on a self-assessment. Patients also underwent the butanol threshold test (BTT), Cross-Cultural Smell Identification Test (CCSIT), and 11-item olfactory questionnaire. Subjects with normosmia preoperatively and who were followed up at least 6 months after surgery were analyzed. Receiver operating characteristic curves and confusion matrix analysis were performed for BTT, CCSIT, and olfactory questionnaire to compare their diagnostic abilities. The effects of age, preoperative olfaction, septal flap, tumor pathology, and tumor size on postoperative olfaction were evaluated using multivariate linear regression analysis. Results: Data from 108 patients were analyzed. Postoperative changes in the olfactory questionnaire were significantly associated with changes in the BTT and CCSIT. The area under the curve for postoperative self-olfactory function classification was highest for olfactory questionnaire (0.894), followed by BTT (0.767) and CCSIT (0.688). Patient age at the time of surgery and preoperative BTT score were significantly related to postoperative olfactory outcomes. Conclusion: The olfactory questionnaire correlated well with conventional psychosomatic olfactory function tests. In combination with clinical parameters and preoperative psychosomatic olfactory function tests, the olfactory questionnaire is suitable for assessing subjective olfactory function after endoscopic endonasal skull base surgery.

Development of a Digital Olfactory Function Test: A Preliminary Study

Olfactory dysfunction is associated with conditions such as neurodegenerative diseases, diabetes, obesity, autoimmune diseases, mental illnesses, and upper-airway-related diseases. The COVID-19 pandemic necessitated the development of an examiner-independent olfactory function test. We recently developed a digital olfactory function test called Digitalscent (DIGITAL SCENT), which is a kiosk-type device with an integrated hardware system. The protocol follows conventional psychophysical olfactory function protocols, including threshold, discrimination, and identification test subsets. Eight healthy participants without olfactory dysfunction volunteered for the suitability test and completed both the YSK olfactory function and Digitalscent tests. Pearson correlations were determined between the YSK olfactory function and Digitalscent tests. Digitalscent could be implemented as a conventional olfactory function test, and all participants followed the Digitalscent test protocols. Limitations in the threshold and identification test subsets included unfamiliarity of the patients to the digital test and incompleteness in the sophisticated release of odorants. A strength of the identification test subset was the dual sensory stimulation of vision and olfaction. Digitalscent could-without facilitating viral transmission-enable early diagnosis of olfactory dysfunction during respiratory viral pandemics. Future studies with larger sample sizes are warranted to facilitate wider use of this digital olfactory function test.

Comparative Olfactory Profiles in Parkinson's Disease and Drug-Induced Parkinsonism

OBJECTIVE

Drug-induced parkinsonism (DIP) is a frequently encountered diagnostic possibility when considering Parkinson's disease (PD). While olfactory dysfunction is a common clinical feature in PD, the comparison of olfactory function between the two conditions remains insufficient. This study aimed to compare olfactory function, including threshold, discrimination, and identification (TDI) profiles, between PD and DIP.

METHODS

Consecutive patients with drug-naïve PD (n = 78) or DIP (n = 31) confirmed through dopamine transporter imaging were enrolled in this study. The YSK olfactory function (YOF) test, composed of TDI domains culturally familiar odorants to Koreans, was administered to all patients.

RESULTS

In the study population, patients with DIP were significantly older than patients with PD. Over 70% of patients in each group had hyposmia or anosmia, and there was no significant difference in the occurrence of olfactory dysfunction between the two groups. In addition, there were no differences in the total YOF score and threshold score between the two groups. Meanwhile, the PD group had a significantly lower discrimination and identification score than the DIP group after adjusting for age, sex, the existence of diabetes, disease duration, and cognitive function.

CONCLUSION

This study demonstrated that detailed olfactory profiles are different in PD and DIP, even though olfactory dysfunction can be observed in both conditions.

Brain olfactory-related atrophy in isolated rapid eye movement sleep behavior disorder

OBJECTIVE

To investigate structural and functional connectivity changes in brain olfactory-related structures in a longitudinal prospective cohort of isolated REM sleep behavior disorder (iRBD) and their clinical correlations, longitudinal evolution, and predictive values for phenoconversion to overt synucleinopathies, especially Lewy body diseases.

METHODS

The cohort included polysomnography-confirmed iRBD patients and controls. Participants underwent baseline assessments including olfactory tests, neuropsychological evaluations, the Movement Disorders Society-Unified Parkinson's Disease Rating Scale, 3T brain MRI, and 18 F-FP-CIT PET scans. Voxel-based morphometry (VBM) was performed to identify regions of atrophy in iRBD, and volumes of relevant olfactory-related regions of interest (ROI) were estimated. Subgroups of patients underwent repeated volumetric MRI and resting-state functional MRI (fMRI) scans after four years.

RESULTS

A total of 51 iRBD patients were included, with 20 of them converting to synucleinopathy (mean time to conversion 3.08 years). Baseline VBM analysis revealed atrophy in the right olfactory cortex and gyrus rectus in iRBD. Subsequent ROI comparisons with controls showed atrophy in the amygdala. These olfactory-related atrophies tended to be associated with worse depression, anxiety, and urinary problems in iRBD. Amygdala 18 F-FP-CIT uptake tended to be reduced in iRBD patients with hyposmia (nonsignificant after multiple comparison correction) and correlated with urinary problems. Resting-state fMRI of 23 patients and 32 controls revealed multiple clusters with aberrant olfactory-related functional connectivity. Hypoconnectivity between the putamen and olfactory cortex was associated with mild parkinsonian signs in iRBD. Longitudinal analysis of volumetric volumetric MRI in 22 iRBD patients demonstrated four-year progression of olfactory-related atrophy. Cox regression analysis revealed that this atrophy significantly predicted phenoconversion.

INTERPRETATION

Progressive atrophy of central olfactory structures may be a potential indicator of Lewy body disease progression in iRBD.

A case of olfactory neuroblastoma that presented with olfactory dysfunction after a COVID-19 diagnosis

Background

Olfactory dysfunction is associated with conditions such as respiratory tract infections, trauma, sinonasal diseases, and neurodegenerative diseases. During the coronavirus disease 2019 pandemic, there was an increase in patients complaining of olfactory dysfunctions. Many studies have reported that olfactory dysfunction is associated with coronavirus disease 2019 and that the prognosis is usually favorable.

Case presentation

Recently, we experienced a patient with olfactory dysfunction, which was aggravated after a coronavirus disease 2019 diagnosis. The patient had no other medical history, and their nasal endoscopic examination demonstrated no abnormal lesions. Through a psychophysical olfactory function test, the patient was diagnosed with anosmia. A paranasal sinus computed tomography demonstrated sclerotic bony changes in the cribriform plate area. A paranasal sinus magnetic resonance image study found an approximately 3.5 cm-sized olfactory neuroblastoma in the anterior cranial fossa.

Conclusions

We suggest clinicians remember the possibility of underlying intracranial lesions in patients with olfactory dysfunction even during the coronavirus disease 2019 pandemic and understand the guidelines of magnetic resonance imaging when evaluating olfactory dysfunction patients. Furthermore, we recommend that clinicians pay attention to the history of olfactory dysfunction before the symptoms progress and making a coronavirus disease 2019 diagnosis.

The PEA Bead Test as a Screening Tool for Olfactory Dysfunction: A Preliminary Study

This study, conducted in a single tertiary hospital, aimed to evaluate the 2-phenylethyl alcohol (PEA)-based sniffing bead test as a screening tool for olfactory dysfunction suitable for implementation in otorhinolaryngology and other settings, including general practice clinics. A total of 139 patients were enrolled, all of whom underwent both the PEA bead test and conventional psychophysical olfactory function testing. Characteristics such as age, sex, concurrent diseases, smoking history, and presence of gustatory dysfunction were reviewed. Statistical analyses included receiver operating characteristic curve analysis, area under the curve determination, and multivariate linear regression guided by the Akaike information criterion. Significant correlations were found between the PEA bead test and various subsets of the conventional YSK olfactory function test: threshold (r = 0.631), discrimination (r = 0.455), and identification (r = 0.596), as well as the composite threshold-discrimination-identification score (r = 0.686). These correlations remained significant even when adjusting for other clinical characteristics. The PEA bead test showed a sensitivity of 0.778 and a specificity of 0.958 for discriminating olfactory dysfunction at a cutoff value of ≥1. These findings indicate that the PEA bead test could be a valuable screening tool for olfactory dysfunction across diverse clinical settings. Further large-scale, multicenter research is recommended to confirm these preliminary results.

Calprotectin in chronic rhinosinusitis eosinophil extracellular traps

BACKGROUND

Calprotectin is an antimicrobial peptide primarily secreted by neutrophils. Furthermore, calprotectin secretion increases in patients with chronic rhinosinusitis (CRS) with polyps (CRSwNP) and positively correlates with neutrophil markers. However, CRSwNP is known to be associated with type 2 inflammation related to tissue eosinophilia. Therefore, the authors investigated calprotectin expression in eosinophils and eosinophil extracellular traps (EETs) and explored the associations between tissue calprotectin and the clinical findings of patients with CRS.

METHODS

A total of 63 patients participated, and patients diagnosed with CRS were classified based on the Japanese Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis (JESREC) score. The authors performed hematoxylin and eosin staining, immunohistochemistry, immunofluorescence with calprotectin, myeloperoxidase (MPO), major basic protein (MBP), and citrullinated histone H3 with the participant's tissues. Finally, correlations between calprotectin and the clinical data were examined.

RESULTS

Calprotectin-positive cells are co-localized not only in MPO-positive cells but also in MBP-positive cells in human tissues. Calprotectin was also involved in EETs and neutrophil extracellular traps. The number of calprotectin-positive cells in the tissue was positively correlated with the number of tissue and blood eosinophils. In addition, calprotectin in the tissue is associated with the olfactory function, Lund-Mackay computed tomography score, and JESREC score.

CONCLUSIONS

Calprotectin, known to be secreted by neutrophils, in CRS was also expressed in eosinophils. In addition, calprotectin, which functions as an antimicrobial peptide, may play an important role in the innate immune response based on its EET involvement. Therefore, calprotectin expression could reflect as a disease severity biomarker for CRS.

Diet quality and prodromal Parkinson's disease probability in isolated REM sleep behavior disorder

INTRODUCTION

It is reported that a diet that lowers oxidative stress reduces the prodromal Parkinson's disease (pPD) probability as well as the risk of Parkinson's disease (PD). In this study, we evaluated whether the diet quality of patients with isolated rapid eye movement (REM) sleep behavior disorder (iRBD) were associated with the pPD probability score, PD risk markers, or prodromal markers.

METHODS

Polysomnography (PSG)-confirmed iRBD patients from the Neurology Department at Seoul National University Hospital were enrolled. We calculated the pPD probability using the "Web-based Medical Calculator for Prodromal Risk in Parkinsonism" Diet quality was assessed using the Recommended Food Score (RFS).

RESULTS

We enrolled 101 patients with iRBD. The mean RFS score of patients with iRBD was 28.23 ± 9.29, which did not differ from the general population. Among patients with iRBD, the probability of pPD did not differ between the high and low RFS groups. In patients aged <70 years, although total RFS was not correlated with pPD probability (p = 0.529, Spearman rank correlation), legume consumption was negatively correlated with pPD probability (p = 0.032): furthermore, legume consumption was significantly higher in patients with fewer prodromal markers (p = 0.016).

CONCLUSION

Diet quality assessed by RFS did not differ between the general population and patients with iRBD in Korea. Further studies are needed to confirm these protective effects of legume consumption on iRBD, which may have strong implications for the prevention and management of PD.

The YSK Olfactory Function Test: Development of a New Korean Olfactory Test

Olfaction is an important aspect of quality of life, beyond simply smelling food and recognizing danger. Recently, research has focused on its association with various diseases, such as neurodegenerative diseases or viral infections. The evaluation of olfactory function must take into consideration the cultural experience of the target group. A new Korean culturefriendly olfactory function test, the YSK olfactory function test (YOF test, Kimex Co.), uses safe odorants, such as phenyl-ethyl alcohol (PEA) (not n-butanol), for the threshold test. Furthermore, odorants in the YOF identification test reflect each of eight major chemical functional groups. The diagnostic cut-off for anosmia was a Threshold Discrimination Identification (TDI) score of ≤14.5 and that for hyposmia was 14.5<TDI≤21.0. The YOF test showed relevant diagnostic validity for olfactory dysfunction when compared with the Korean version of the Sniffin’ Stick-II test. In this review, we share our experiences developing a new Korean-friendly olfactory function test.

Gustatory dysfunction in patients with olfactory dysfunction and the associated factors

BACKGROUND

Little is known about the occurrence of gustatory dysfunction (GD) in relation to different aetiologies of olfactory dysfunction (OD) as assessed by psychophysical chemosensory tests. The aim of this study was to analyse gustatory function in patients with OD and to investigate clinical factors associated with GD.

METHODS

A total of 742 individuals who underwent both olfactory and gustatory function tests at a tertiary medical centre from November 2019 to March 2021 were retrospectively enrolled. Olfactory and gustatory function were assessed by the YSK olfactory and gustatory function tests, respectively. Patients with OD were classified into four groups according to the aetiology: sinonasal disease, post-infection OD (PIOD), post-traumatic OD (PTOD), and others. Secondary outcomes included age, sex, smoking history, and alcohol history.

RESULTS

Among the 488 patients with OD, 93 (19.1%) showed GD and 395 (80.9%) had normal gustatory function. Only 25 (9.8%) among 254 individuals with normosmia showed GD. Analyses of these frequencies revealed a significant association between OD and GD. In addition, the taste score was significantly lower in patients with OD than individuals with normosmia. The frequency of GD was significantly higher in patients with PTOD (53.6%) than in those with OD of other aetiologies (sinonasal disease, 6.7%; PIOD, 13.0%; others, 24.4%). In the multivariate analysis, age ≥55 years and PTOD were associated with a high frequency of GD among patients with OD.

CONCLUSIONS

The current study show that GD is significantly associated with OD. In particular, GD is more common in patients with PTOD than in those with OD of other aetiologies.

Effect of intensive olfactory training for cognitive function in patients with dementia

AIM

Recent evidence has revealed an association between neurodegenerative disorders and olfactory dysfunction. However, whether olfactory training can improve cognitive impairment in patients with dementia requires further study. The present study aimed to resolve this by developing an intensive olfactory training (IOT) protocol and assessing its impact on each of the cognitive domains in patients with dementia.

METHODS

Patients were prospectively recruited between June 2020 and September 2020. Baseline evaluations included demographic data, olfactory function test, depression scale and detailed cognitive function tests. Thirty-four patients in the experimental group underwent IOT twice a day with a 40-odor set for 15 days, while 31 individuals in the control group received conservative management. Follow-up evaluations using the depression scale and detailed cognitive function tests were performed after IOT.

RESULTS

Baseline characteristics were not different between the two groups. The IOT group showed significant improvements in depression, attention, memory and language functions, but not global cognition, frontal executive, or visuospatial functions compared with the control group.

CONCLUSION

This study shows the ability of IOT to alleviate depression and improve some cognitive functions in patients with dementia. These results suggest that IOT may be an effective non-pharmacological approach for improving the symptoms of dementia. Geriatr Gerontol Int ••; ••: ••-•• Geriatr Gerontol Int 2021; ••: ••-••.

Association Between Olfactory Function and Asthma in Adults

Purpose

Chronic rhinosinusitis (CRS) and allergic rhinitis (AR) are common asthma-associated upper airway diseases. Olfactory dysfunction, a common symptom among these patients, is an increasingly recognized condition that is associated with a reduced quality of life and major health outcomes. However, there are few studies on the association between olfactory function and asthma. We investigated the relationship between asthma and olfactory function.

Patients and Methods

A total of 146 patients with asthma aged >18 years were retrospectively analyzed from August 2019 to February 2020. Olfactory function was assessed using the Sniffin' stick test or the YSK olfactory function test. We compared the clinical parameters of patients with olfactory dysfunction and patients with normosmia.

Results

Of the total participants, 68 (46.6%) showed olfactory dysfunction (hyposmia, n=31; anosmia, n=37). The patients with olfactory dysfunction were older, had longer durations of asthma, and a higher proportion of those with poor general health, CRS, and nasal polyps compared to patients with normosmia. However, there were no significant differences in the socioeconomic status, lung function, asthma severity, and use of inhaled corticosteroids or intranasal steroids between the two groups. Age (odds ratio: 1.044, 95% confidence interval: 1.009-1.081, P=0.012), poor general health (3.304, 1.231-8.863, P=0.018), CRS (2.589, 1.155-5.804, P=0.021), and nasal polyps (3.306, 1.1-9.94, P=0.033) were significantly associated with olfactory dysfunction.

Conclusion

Olfactory dysfunction was quite frequently observed in adults with asthma. Age, poor general health, CRS, and nasal polyps were significantly associated with olfactory dysfunction.