Psychophysical Testing in Chemosensory Disorders

A practical test for retronasal odor identification based on aromatized tablets

BACKGROUND

Olfactory perceptions elicited by odors originating from within the body (retronasal olfaction) play a crucial role in well-being and are often disrupted in various medical conditions. However, the assessment of retronasal olfaction in research and the clinical practice is impeded by the lack of commercially available tests and limited standardization of existing testing materials.

NEW METHOD

The novel ThreeT retronasal odor identification test employs 20 flavored tablets that deliver a standardized amount of odorous stimuli. The items represent common food- and non-food-related odors.

RESULTS

The ThreeT test effectively distinguishes patients with olfactory dysfunction from healthy controls, achieving a specificity of 86% and sensitivity of 73%. Its scores remain stable for up to 3 months (r=.79).

COMPARISON WITH EXISTING METHOD

ThreeT test exhibits a strong correlation with "Tasteless powders" measure of retronasal olfaction (r=.78) and classifies people into healthy and patient groups with similar accuracy. Test-retest stability of ThreeT is slightly higher than the stability of "Tasteless powders" (r=.79 vs r=.74).

CONCLUSIONS

ThreeT is suitable for integration into scientific research and clinical practice to monitor retronasal odor identification abilities.

International clinical assessment of smell: An international, cross-sectional survey of current practice in the assessment of olfaction

OBJECTIVES

Olfactory dysfunction (OD) is common and carries significant personal and societal burden. Accurate assessment is necessary for good clinical and research practice but is highly dependent on the assessment technique used. Current practice with regards to UK/international clinical assessment is unknown. We aimed to capture current clinical practice, with reference to contemporaneously available guidelines. We further aimed to compare UK to international practice.

DESIGN

Anonymous online questionnaire with cross-sectional non-probability sampling. Subgroup analysis according to subspeciality training in rhinology ('rhinologists' and 'non-rhinologists') was performed, with geographical comparisons only made according to subgroup.

PARTICIPANTS

ENT surgeons who assess olfaction.

RESULTS

Responses were received from 465 clinicians (217 from UK and 17 countries total). Country-specific response rate varied, with the lowest rate being obtained from Japan (1.4%) and highest from Greece (72.5%). Most UK clinicians do not perform psychophysical smell testing during any of the presented clinical scenarios-though rhinologists did so more often than non-rhinologists. The most frequent barriers to testing related to service provision (e.g., time/funding limitations). Whilst there was variability in practice, in general, international respondents performed psychophysical testing more frequently than those from the UK. Approximately 3/4 of all respondents said they would like to receive training in psychophysical smell testing. Patient reported outcome measures were infrequently used in the UK/internationally. More UK respondents performed diagnostic MRI scanning than international respondents.

CONCLUSIONS

To our knowledge, this is the most comprehensive UK-based, and only international survey of clinical practice in the assessment of OD. We present recommendations to improve practice, including increased education and funding for psychophysical smell testing. We hope this will promote accurate and reliable olfactory assessment, as is the accepted standard in other sensory systems.

Patient Experience and Preferences for the Assessment of Olfaction: The Patient International Clinical Assessment of Smell Survey

INTRODUCTION

Olfactory dysfunction (OD) is common and carries significant personal and societal burden of disease. Accurate assessment of olfaction is required for good clinical care and affords patients insight into their condition. However, the accuracy of assessment varies with technique used, and there is presently little standardisation of clinical practice. We therefore aimed to determine experience of and preferences for olfactory assessment in healthcare-seeking adults.

METHODS

An anonymous patient co-produced survey was developed in collaboration with a UK-based OD charity. Distribution was via their social media patient forum. "Healthcare seeking" adults (i.e., who had undergone olfactory assessment by a healthcare professional [any care level/speciality] or may do so in the future) were included.

RESULTS

576 people (88.5% female, mean 46 years) responded. Hyposmia, parosmia, and retronasal OD were most frequently reported. 55.2% had been assessed by a healthcare professional - GP most commonly, followed by ENT. Importantly, only 15.6% and 16.9% of respondents had undergone systematic assessment with smell tests or symptom questionnaires, respectively. Most respondents had not undergone imaging. Mean satisfaction was higher in those seen by ENT. Interestingly, respondents prioritise orthonasal odour identification over other forms of smell test. Unfortunately, many felt that healthcare professionals (across specialities) were dismissive towards OD and lacked appropriate knowledge of both its pathophysiology and effects. We propose simple steps that can be taken to improve olfactory assessment, including education and establishment of robust referral networks.

CONCLUSION

We hope these results and supporting practical recommendations will inform future service planning, funding allocation and research, as well as better aligning patient and clinician priorities.

Functional septorhinoplasty alters brain structure and function: Neuroanatomical correlates of olfactory dysfunction

Introduction

We previously demonstrated functionally significant structural plasticity within the central olfactory networks, in association with improved olfaction after surgical treatment of chronic rhinosinusitis (CRS). In order to confirm and expand on these findings, the primary aim of this study was to determine whether these same regions undergo functionally significant structural plasticity following functional septorhinoplasty (fSRP), in patients with non-CRS olfactory dysfunction (OD) of mixed cause. fSRP has previously been shown to improve olfactory function, and the secondary aim of this study was to provide initial insights into the mechanism by which fSRP affects olfaction.

Methods

We performed a pilot prospective, multimodal neuroimaging study in 20 participants undergoing fSRP, including patients with non-CRS OD of mixed cause, as well as normosmic surgical controls. Participants underwent psychophysical olfactory testing, assessment of nasal airway, structural and functional neuroimaging. This was performed pre- and postoperatively in patients, and preoperatively in controls.

Results

There was a statistically and clinically significant improvement in mean psychophysical olfactory scores after surgery. This was associated with structural and functional plasticity within areas of the central olfactory network (anterior cingulate, orbitofrontal cortex, insula, temporal pole). Improved psychophysical scores were significantly correlated with change in bilateral measures of nasal airflow, not measures of airflow symmetry, suggesting that improved overall airflow was more important than correction of septal deviation.

Conclusion

This work highlights the importance of these neuroanatomical regions as potential structural correlates of olfactory function and dysfunction. Our results also provide initial insight into the mechanistic effects of fSRP on olfaction. Further work could investigate the utility of these regions as personalised biomarkers of OD, as well as the role of fSRP in treating OD.

Prevalence of Olfactory Dysfunction with the Omicron Variant of SARS-CoV-2: A Systematic Review and Meta-Analysis

The omicron variant is thought to cause less olfactory dysfunction than previous variants of SARS-CoV-2, but the reported prevalence differs greatly between populations and studies. Our systematic review and meta-analysis provide information regarding regional differences in prevalence as well as an estimate of the global prevalence of olfactory dysfunction based on 62 studies reporting information on 626,035 patients infected with the omicron variant. Our estimate of the omicron-induced prevalence of olfactory dysfunction in populations of European ancestry is 11.7%, while it is significantly lower in all other populations, ranging between 1.9% and 4.9%. When ethnic differences and population sizes are considered, the global prevalence of omicron-induced olfactory dysfunction in adults is estimated to be 3.7%. Omicron's effect on olfaction is twofold to tenfold lower than that of the alpha or delta variants according to previous meta-analyses and our analysis of studies that directly compared the prevalence of olfactory dysfunction between omicron and previous variants. The profile of the prevalence differences between ethnicities mirrors the results of a recent genome-wide association study that connected a gene locus encoding an odorant-metabolizing enzyme, UDP glycosyltransferase, to the extent of COVID-19-related loss of smell. Our analysis is consistent with the hypothesis that this enzyme contributes to the observed population differences.