Self-Ratings of Olfactory Performance and Odor Annoyance Are Associated With the Affective Impact of Odor, but Not With Smell Test Results

Giving a Voice to Patients With Smell Disorders Associated With COVID-19: Cross-Sectional Longitudinal Analysis Using Natural Language Processing of Self-Reports

BACKGROUND

Smell disorders are commonly reported with COVID-19 infection. The smell-related issues associated with COVID-19 may be prolonged, even after the respiratory symptoms are resolved. These smell dysfunctions can range from anosmia (complete loss of smell) or hyposmia (reduced sense of smell) to parosmia (smells perceived differently) or phantosmia (smells perceived without an odor source being present). Similar to the difficulty that people experience when talking about their smell experiences, patients find it difficult to express or label the symptoms they experience, thereby complicating diagnosis. The complexity of these symptoms can be an additional burden for patients and health care providers and thus needs further investigation.

OBJECTIVE

This study aims to explore the smell disorder concerns of patients and to provide an overview for each specific smell disorder by using the longitudinal survey conducted in 2020 by the Global Consortium for Chemosensory Research, an international research group that has been created ad hoc for studying chemosensory dysfunctions. We aimed to extend the existing knowledge on smell disorders related to COVID-19 by analyzing a large data set of self-reported descriptive comments by using methods from natural language processing.

METHODS

We included self-reported data on the description of changes in smell provided by 1560 participants at 2 timepoints (second survey completed between 23 and 291 days). Text data from participants who still had smell disorders at the second timepoint (long-haulers) were compared with the text data of those who did not (non-long-haulers). Specifically, 3 aims were pursued in this study. The first aim was to classify smell disorders based on the participants' self-reports. The second aim was to classify the sentiment of each self-report by using a machine learning approach, and the third aim was to find particular food and nonfood keywords that were more salient among long-haulers than those among non-long-haulers.

RESULTS

We found that parosmia (odds ratio [OR] 1.78, 95% CI 1.35-2.37; P<.001) as well as hyposmia (OR 1.74, 95% CI 1.34-2.26; P<.001) were more frequently reported in long-haulers than in non-long-haulers. Furthermore, a significant relationship was found between long-hauler status and sentiment of self-report (P<.001). Finally, we found specific keywords that were more typical for long-haulers than those for non-long-haulers, for example, fire, gas, wine, and vinegar.

CONCLUSIONS

Our work shows consistent findings with those of previous studies, which indicate that self-reports, which can easily be extracted online, may offer valuable information to health care and understanding of smell disorders. At the same time, our study on self-reports provides new insights for future studies investigating smell disorders.

The relationship between survey-based subjective olfactory awareness and objective olfactory function

KEY POINTS

Correlation between symptom-based surveys and objective olfactory testing is variable. For diagnosis and symptom monitoring, surveys should correlate with objective testing. The Odor Awareness Scale (OAS) and Affective Importance of Odor Scale (AIO) showed significant but moderate positive correlations with University of Pennsylvania Scent Identification Test (UPSIT) score.

Validation of Minimal Clinically Important Difference (MCID) for University of Pennsylvania Smell Identification Test (UPSIT)

BACKGROUND

The University of Pennsylvania Smell Identification Test is widely used to measure change in olfactory function, but a minimal clinically important difference (MCID) has not been well-established. A study published in 1997 regarding patients with head trauma reported an MCID of 4 but did not detail the methods used in the calculation.

OBJECTIVE

To validate the MCID for UPSIT in patients with postviral, sinusitis, and procedure-associated olfactory loss.

METHODS

This was a secondary analysis of prospectively collected data from 5 clinical research studies related to olfactory function. Three studies included subjects with COVID-19-related olfactory dysfunction, one with chronic sinusitis subjects, and one with subjects undergoing transsphenoidal surgery. All subjects had completed a baseline and follow-up UPSIT, baseline and follow-up Clinical Global Impression-Severity (CGI-Severity), and a follow-up CGI-Improvement. Both distribution- and anchor-based methods were used to determine the MCID of UPSIT. Distribution-based method calculated MCID using half standard deviation of baseline UPSIT and delta UPSIT scores. Clinical-anchor method determined MCID by comparing delta UPSIT scores between consecutive CGI-I clinical categories ranging from very much better to very much worse.

RESULTS

The study population comprised 295 subjects. Subjects had a mean (SD) baseline UPSIT score of 27 (7.5), and follow-up score of 28 (7.9), and a mean UPSIT change of 0.6 (5.8). Half the baseline UPSIT SD was 3.75 and half the delta UPSIT SD was 2.9. With the anchor-based approach, an MCID of 4 was defined as clinically meaningful by exploring the relationship between delta UPSIT and CGI-Improvement. Using a more conservative approach based on the MCID values identified from both methods, we determined that a change of 4 or greater is the appropriate MCID for UPSIT.

CONCLUSION

Investigators in the future should use 4 as MCID for UPSIT and report the percentage of study subjects who achieve a clinically meaningful difference.

LEVEL OF EVIDENCE

III.

Olfactory metacognition and memory in individuals with different subjective odor imagery abilities

Imagery vividness is one of the key indicators to evaluate the ability to generate mental images. There is large inter-individual variability in olfactory imagery (OI) abilities, however, little is known about the underlying factors for individual OI abilities. Using a word cueing imagery paradigm and the trial-by-trial imagery vividness rating method, participants with high or low OI abilities (differentiated by the Vividness of Olfactory Imagery Questionnaire) completed two OI tasks with either shorter (2 s) or longer (8 s) image generation time. Participants' olfactory function, olfactory-related working memory and episodic recognition memory were measured using validated methods. Moreover, olfactory metacognition was assessed using the Odor Awareness Scale (OAS) and the Importance of Olfaction Questionnaire (IOQ). Compared to participants with high OI abilities, those with low OI abilities reported less vivid odor images during OI tasks. For participants with low OI abilities, the imagery vividness significantly improved as the image generation time increased. There was no difference regarding olfactory perception or olfactory-related memory performances between the high and the low OI ability groups. However, participants with higher OI abilities had significant higher scores on the OAS and the IOQ, indicating a superior olfactory-related metacognition. These results provide evidences supporting the underlying factors that related to variances of subjective ability of generating vivid odor mental images.

Psychophysical Testing in Chemosensory Disorders

Purpose of Review

To provide an overview of psychophysical testing in olfaction and gustation.

Recent Findings

Subjective patient report correlates poorly with objective assessment of olfaction and gustation. It is therefore important that clinicians and researchers perform psychophysical testing during chemosensory assessment. There are several validated psychophysical tests of olfaction and gustation, with ongoing developments accelerated by the COVID-19 pandemic. These tests have been culturally and linguistically adapted globally. Screening tests have been developed with careful consideration to distinguish normosmics from those with olfactory dysfunction.

Summary

Validated chemosensory tools are available for use by the clinician to support screening, diagnosis, or monitoring. There are promising advances in self-assessment and screening that provide avenues for the development of a standardised pathway for identification and formal assessment of patients with smell and taste disorders.

Odor Identification by Parkinson’s Disease Patients Tested by Using Sniffin’ Sticks versus Natural Spices

Introduction

Hyposmia is a frequent symptom of Parkinson's disease (PD), which greatly impacts patients' flavor perception and their quality of life. However, PD patients recognize some odors better than others. Identifying which food odors are still recognized by PD patients may be useful for flavor enhancement. Our aim was to evaluate the olfactory identification of Sniffin' Sticks and spice odorants in PD patients and healthy controls (HC), to identify the impact of synthetic odorants compared with real-life food and the impact of odor familiarity and pleasantness on odorant identification in PD patients.

Methods

Sniffin' Sticks odorant identification was evaluated in 80 PD patients and 105 age-matched HC. In a subset, the spice odorant identification was evaluated.

Results

The mean total score was higher for the Sniffin' Sticks than for the spice odor identification test in all participants (55.4% versus 22.5%). Sniffin' Sticks orange, peppermint, rose, and fish odorants were best correctly identified by PD patients, by 62.5, 53.8, 52.9, and 57.5%, respectively. Of the spice odor identification test, garlic and “no stimulus” were best correctly identified by PD patients, by, respectively, 38.2 and 67.6%. HC identified most Sniffin' Sticks odorants and spices better than PD patients. Odorant familiarity determined real-life food odorant identification.

Conclusion

This study demonstrates that some food odorants, both the commercial Sniffin' Sticks as natural odorants, are still recognized by PD patients. Sniffin' Sticks were better recognized compared with real-life odorants, by both HC and PD patients. Odorant familiarity determined PD patients' odorant identification; therefore, familiar food odorants may have potential for a future flavor enhancement. Implications. This is the first study, to our knowledge, to evaluate real-life food odor identification in PD patients. Our results provide a first step towards patient-appropriate flavor enhancement strategies in PD.

A Pilot Study of Self-Rated and Psychophysical Olfactory Dysfunction in Men Living with HIV

Background

Olfactory loss is associated with poor quality of life, malnutrition, and increased risk of depression, yet few studies have examined unawareness of olfactory dysfunction in men living with HIV (MLWH).

Method

MLWH (n = 51) completed olfaction self-ratings, psychophysical odor identification testing, cognitive measures, and questionnaires assessing smell habits, mood, cognitive failures, and quality of life. The sensitivity and specificity of olfactory self-ratings was calculated, and t-tests were used to examine factors contributing to discordance between self-rated and psychophysical olfaction dysfunction.

Results

We found that 33.3% (17 of 51 MLWH) of our sample demonstrated discordance between self-reported and psychophysical olfactory scores. Those unaware of olfaction dysfunction reported using less scented products in daily life but showed no other differences across demographic, clinical, or cognitive indices.

Conclusions

Our results cohere with prior studies of cognitively normal older adults, traumatic brain injury, and Parkinson's disease, which found that olfactory self-ratings may inadequately capture the full range of a person's olfactory status. Our work extends these findings to MLWH, with discordance rates ranging from 35 to 61% for self-rated and psychophysical olfactory dysfunction.

Implications

Given the differing rates of self-rated and psychophysical olfaction in our sample, psychophysical olfactory measures may be useful to consider in the neuropsychological assessment and clinical care of PLWH.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12078-022-09305-x.

Smell and taste in idiopathic blepharospasm

The pathophysiology of blepharospasm is incompletely understood. Current concepts suggest that blepharospasm is a network disorder, involving basal ganglia, thalamus, cortex, and, possibly, the cerebellum. Tracing, imaging, and clinical studies revealed that these structures are also concerned with olfaction and taste. Because of this anatomical overlap, dysfunction of the chemical senses in blepharospasm is expected. Injections of botulinum toxin into the eyelid muscles are the first-line treatment of blepharospasm. Yet, the effects of botulinum toxin on the chemical senses have not been systematically assessed. To contribute to a better understanding of blepharospasm, olfactory and gustatory abilities were assessed in 17 subjects with blepharospasm and 17 age-/sex-matched healthy controls. Sniffin Sticks were used to assess odor threshold, odor discrimination, and odor identification. Results of these three Sniffin Sticks subtests were added to the composite olfactory score. The Taste Strips were applied to assess taste. In an adjacent study, we assessed the sense of smell and taste in eight subjects with blepharospasm before and 4 weeks after botulinum toxin treatment. Subjects with blepharospasm had significantly lower (= worse) scores for odor threshold and for the composite olfactory score than healthy controls, while odor discrimination, odor identification, and the composite taste score were not different between groups. The adjacent study revealed that botulinum toxin did not impact the chemical senses. In this study, subjects with blepharospasm had a lower (= worse) odor threshold than healthy controls. As olfaction is important in daily life, findings justify further research of olfaction in blepharospasm.

Invalid Self-Assessment of Olfactory Functioning in Parkinson's Disease Patients May Mislead the Neurologist

Olfactory dysfunction (OD) is a prominent nonmotor symptom in Parkinson's disease (PD), and OD is a supportive diagnostic criterion for PD. Physicians often ask their patients if they have noticed a smell disorder. This study evaluates the diagnostic validity of OD self-assessment in PD. To this end, 64 PD patients and 33 age-matched healthy controls were enrolled in a study assessing subjective and objective olfactory functioning. To examine subjective olfactory abilities, first, patients and controls had to classify their olfactory sense as “impaired” or “unimpaired,” comparable to a realistic situation in an outpatient setting. Second, to evaluate subjective olfactory acuity, a visual analogue scale (VAS) was used. Third, the Sniffin' Sticks test battery was used as an objective instrument to diagnose OD. Categorical olfactory self-assessment predicts the classification normosmic versus hyposmic based on the global Sniffin' Sticks score (TDI) with a sensitivity of 0.79 and a specificity of 0.45. TDI correlated significantly with the VAS (r = 0.297, p = 0.017). The ROC curve analysis, using the VAS rating as a predictor for objective olfaction, revealed 42 as the best possible cutoff score with an area under the curve of 0.63. These results demonstrate that olfactory self-assessments show a low accuracy and are not suitable for the diagnosis of a smell disorder in PD. Objective measures are necessary to evaluate olfactory sense in clinical and research settings.

Greater hippocampal gray matter volume in subjective hyperosmia: a voxel-based morphometry study

Subjective hyperosmia refers to a self-reported olfactory ability that is superior to a normal, intact sense of smell (normosmia), and is associated with olfactory emotional experience. The current study used voxel-based morphometry to investigate the gray matter volume (GMV) in people with self-rated hyperosmia (subjective hyperosmia, SH, N = 18) in comparison to people with self-rated normal olfaction (subjective normosmia, SN, N = 14). Participants’ olfactory function were assessed by the extensive olfactory test battery, the “Sniffin’ Sticks” test. Within the predicted brain regions (regions-of-interest analyses), the SH participants showed larger GMV of the left hippocampus as compared to SN participants (FWE corrected p < 0.05). Further, the whole-brain search indicated that SH had larger GMV of the bilateral hippocampus, the right hypothalamus, the left precuneus, and the left superior frontal gyrus as compared to the SN group. ROI analyses showed positive correlations between the left hippocampal GMV and odor threshold or discrimination scores across all participants. In addition, the whole-brain analysis suggested that the self-rated olfactory ability was positively associated with GMV in the cerebellum, superior frontal gyrus and the precentral gyrus among SH participants. In conclusion, the current results suggest that SH was associated with increased GMV in several brain regions that were previously shown to be involved in the processing of cognitive aspects of odors.

Olfactory Characterization of Typical Odorous Pollutants Part I: Relationship Between the Hedonic Tone and Odor Concentration

The hedonic tone is a suitable evaluation index which can truly reflect the psychological impact of an odor. To find out the relationship between the odor concentration (OC) and hedonic tone (H), dimethyl disulfide, limonene and butyl acetate were presented as typical odorants with different characters. A panel of 16 persons was engaged to rate the hedonic tone of a series sample with various concentrations according to the nine-point scale. The relationship between the hedonic tone and OC was established based on a multivariate logistic regression analysis. The research results demonstrated that the smell of dimethyl disulfide is unpleasant at various concentration levels, and its perceived unpleasantness is increased with OC, and at the critical point (H = −0.5), the odor index of dimethyl disulfide is 0.5 (OC = 3 OUE·m−3). For limonene, its smell is pleasant when the odor index is between 1.4 and 3.3 (OC = 25~1995 OUE·m−3). For butyl acetate, the average results showed an unpleasant character with the corresponding odor index of 1.87 (OC = 74 OUE·m−3). Each odorant has a unique hedonic behavior curve from which the annoyance potential of different odorants can be clearly discriminated, with the order of dimethyl disulfide > butyl acetate > limonene. The regression equations showed a quadratic nonlinear function between the hedonic tone and OC.

Olfactory assessment in the Chinese pediatric population

Young children with olfactory disturbance are sometimes encountered in ENT clinics. We investigated the clinical applicability of olfactory testing to the pediatric population in China.One hundred and ninety-three healthy children aged 6 to 17 years were enrolled. All participants were asked for demographic information (age, sex, body mass index [BMI], and rating of olfactory function) in a structured questionnaire and underwent olfactory testing including T&T Olfactometer (T&T), odor discrimination (OD), and odor identification (OI) tests of Sniffin' Sticks.Age had a significant influence on the outcome of olfactory testing, sex, BMI, or self-rating had no influence. Children had better performance on T&T than OI and OD tests of Sniffin' Sticks.T&T and Sniffin' Sticks can be completed by Chinese children. Performance on olfactory tests increased with increasing age. T&T may be more suitable to assess olfactory function in the Chinese pediatric population.