Persisting olfactory dysfunction in post-COVID-19 is associated with gustatory impairment: Results from chemosensitive testing eight months after the acute infection

A Nationwide survey of safety protocols and chemosensory assessments by Japanese clinicians pre- and post-COVID-19 pandemic

OBJECTIVE

There has been an increase of attention and awareness of smell and taste loss due to the impact of COVID-19. However, little is known about the influence of COVID-19 on the number of psychophysical tests performed, the timing of these tests, or the protection protocols employed to protect against virus transmission. This study aimed to explore the changes in examination approaches, types of tests employed, and safety measures adopted by clinicians before and after the COVID-19 pandemic.

METHODS

A survey was distributed to 404 institutes of the Oto-Rhino Laryngological Society of Japan, consisting of otolaryngologists working in university hospitals, general hospitals, and private clinics. The anonymous online survey contained questions related to safety measures and chemosensory assessments performed before and after the COVID-19 pandemic. Specifically, participants were queried on the number and types of examinations conducted, the type of examiners who performed them, the timing of tests in suspected and non-suspected COVID-19 cases, modifications made due to the pandemic, and the protective measures adopted during chemosensory examinations.

RESULTS

Of the 201 respondents, representing a 50 % response rate, 49 % were from general hospitals, 48 % from university hospitals, and 3 % from private clinics. The study found a slight decrease in the overall number of chemosensory tests conducted post-COVID-19. In terms of who performed the test, there were no differences pre- and post- COVID-19. Most examinations (52-68 %) for suspected COVID-19 cases were performed 1-2 months after the onset of symptoms. Modifications in testing rooms and personal protective equipment (PPE) were reported by the majority of institutions post-pandemic. While different examination rooms or PPE were not commonly used based on a patient's previous COVID-19 diagnosis, changes were observed in testing practices. Most examinations were conducted in rooms with windows or fans, and PPE usage was high; surgical masks, eye visors or face shields, and disposable gloves being commonly used. Virus transmission from patient to examiner was reported in only one case during T&T olfactometer examination.

CONCLUSION

We investigated the impact of the COVID-19 pandemic on the number of olfactory and gustatory tests performed, the type of examiner, the examination room, and the use of PPE and found no significant difference before and after the COVID-19 pandemic on these factors. Adherence to a protection protocol involving the proper use of PPE in controlled environments enabled the continuation of olfactory and gustatory tests during the pandemic.

Using SCENTinel® to predict SARS-CoV-2 infection: insights from a community sample during dominance of Delta and Omicron variants

Introduction

Based on a large body of previous research suggesting that smell loss was a predictor of COVID-19, we investigated the ability of SCENTinel®, a newly validated rapid olfactory test that assesses odor detection, intensity, and identification, to predict SARS-CoV-2 infection in a community sample.

Methods

Between April 5, 2021, and July 5, 2022, 1,979 individuals took one SCENTinel® test, completed at least one physician-ordered SARS-CoV-2 PCR test, and endorsed a list of self-reported symptoms.

Results

Among the of SCENTinel® subtests, the self-rated odor intensity score, especially when dichotomized using a previously established threshold, was the strongest predictor of SARS-CoV-2 infection. SCENTinel® had high specificity and negative predictive value, indicating that those who passed SCENTinel® likely did not have a SARS-CoV-2 infection. Predictability of the SCENTinel® performance was stronger when the SARS-CoV-2 Delta variant was dominant rather than when the SARS-CoV-2 Omicron variant was dominant. Additionally, SCENTinel® predicted SARS-CoV-2 positivity better than using a self-reported symptom checklist alone.

Discussion

These results indicate that SCENTinel® is a rapid assessment tool that can be used for population-level screening to monitor abrupt changes in olfactory function, and to evaluate spread of viral infections like SARS-CoV-2 that often have smell loss as a symptom.

Remote psychophysical testing of smell in patients with persistent olfactory dysfunction after COVID-19

Olfactory dysfunction associated with coronavirus 2 (SARS-CoV-2) infection is in most cases transient, recovering spontaneously within a few days. However, in some patients it persists for a long time, affects their everyday life and endangers their health. Hence, we focused on patients with persistent loss of smell. The aim of this study was to evaluate olfactory dysfunction using a standardized test. Due to the pandemic, olfactory testing was performed online. Smell tests (Odorized Markers Test, OMT) were sent home to the patients. Together with the smell self-testing, participants reported and assessed several parameters (age, sex, subjective assessment of smell and taste, nasal patency, etc.) in an online questionnaire. Based on the questionnaire outcomes, the results were sent to the patients along with a list of participating otolaryngologists who provided them with professional care. From March to June 2021, 1025 patients requested smell testing, of these, 824 met the inclusion criteria of this study. The duration of the olfactory dysfunction at the time of testing ranged from 1 month to 1 year. Using the OMT, impaired smell ability-anosmia or hyposmia-was confirmed in 82.6% of participants. A total of 17.4% of participants were determined to be normosmic however, more than 50% of them complained of parosmia and/or phantosmia. Our study demonstrates the relevance of psychophysical smell testing and its suitability for remote use during the pandemic. This study also revealed several correlations between prolonged olfactory dysfunction and the monitored parameters.

Long COVID: An approach to clinical assessment and management in primary care

Long COVID is an emerging public health threat, following swiftly behind the surges of acute infection over the course of the COVID-19 pandemic. It is estimated that there are already approximately 100 million people suffering from Long COVID globally, 0.5 million of whom are South African, and for whom our incomplete understanding of the condition has forestalled appropriate diagnosis and clinical care. There are several leading postulates for the complex, multi-mechanistic pathogenesis of Long COVID. Patients with Long COVID may present with a diversity of clinical phenotypes, often with significant overlap, which may exhibit temporal heterogeneity and evolution. Post-acute care follow-up, targeted screening, diagnosis, a broad initial assessment and more directed subsequent assessments are necessary at the primary care level. Symptomatic treatment, self-management and rehabilitation are the mainstays of clinical care for Long COVID. However, evidence-based pharmacological interventions for the prevention and treatment of Long COVID are beginning to emerge. This article presents a rational approach for assessing and managing patients with Long COVID in the primary care setting.

COVID-19 Oral Sequelae: Persistent Gustatory and Saliva Secretory Dysfunctions after Recovery from COVID-19

Diverse manifestations have been recognized to last for a long time in patients infected with SARS-CoV-2. However, understanding of oral sequelae after recovery from COVID-19 is relatively poor compared to that of oral symptoms in the acute phase of COVID-19 and other COVID-19 sequelae. The aim of the present study was to characterize persistent gustatory and saliva secretory dysfunctions and to speculate on their pathogenic mechanisms. Articles were retrieved by searching scientific databases with a cutoff date of September 30, 2022. The literature search indicated that ageusia/dysgeusia and xerostomia/dry mouth are reported by 1-45% of COVID-19 survivors at follow-ups of 21-365 days and by 2-40% of COVID-19 survivors at follow-ups of 28-230 days, respectively. The prevalence of gustatory sequelae partly depends on difference in ethnicity, gender, age, and disease severity of subjects. Co-occurring gustatory and saliva secretory sequelae are pathogenically related to either or both of the following: expression of SARS-CoV-2 cellular entry-relevant receptors in taste buds and salivary glands, and SARS-CoV-2 infection-induced deficiency in zinc that is essential for normality of taste perception and saliva secretion. Given the long-term oral sequelae, hospital discharge is not the end of the disease; therefore, careful attention should be continuously paid to oral conditions of post-COVID-19 patients.

Prevalence of olfactory dysfunction in D614G, alpha, delta and omicron waves: a psychophysical case-control study

BACKGROUND

The purpose of this study was to compare the prevalence of olfactory dysfunction (OD) at different stages of the COVID-19 pandemic by evaluating subjects diagnosed with SARS-CoV-2 infection during the Omicron wave with psychophysical tests and comparing the results with those obtained from patients infected during the D614G, Alpha and Delta waves and with those of a control group.

METHODOLOGY

The study included adult patients diagnosed with SARS-CoV-2 infection. Depending on the time of diagnosis, the subjects were divided into four study groups: D614G; Alpha, Delta and Omicron variant groups. A group of uninfected individuals was used as control. All subjects underwent psychophysical evaluation of the olfactory function with the Connecticut Chemosensory Clinical Research Center olfactory test (D614G and Alpha groups) or the extended version of the Sniffin'Sticks test (Delta, Omicron and control groups).

RESULTS

372 cases (134 D614G group, 118 Alpha group, 32 in Delta group and 88 Omicron group) were recruited and evaluated within 10 days of infection, alongside 80 controls. Patients self-reported olfactory loss in 72.4% of cases in the D614G group, in 75.4% of cases in the Alpha group, in 65.6% of cases in the Delta group and in 18.1% in the Omicron group. Psychophysical evaluation revealed a prevalence of OD: 80.6%, 83.0%, 65.6% and 36.3% in the D614G, Alpha, Delta and Omicron group respectively. The differences between the D614G, Alpha and Delta groups were not statistically significant. The Omicron group demonstrated a significantly lower prevalence of OD than the other variants but still significantly higher than the controls.

CONCLUSIONS

During the Omicron wave OD was less prevalent than during the D614G, Alpha and Delta periods. One-third of patients have reduced olfactory function on psychophysical evaluation during the Omicron wave. Our results should be considered with caution as the VOC has not been determined with certainty.

Long-term Consequences of COVID-19: Chemosensory Disorders

PURPOSE OF REVIEW

A number of sequelae after acute coronavirus disease 2019 (COVID-19) significantly affect the quality of life of patients. The chemosensory disorders including olfactory dysfunction (OD) and gustatory dysfunction (GD) are two of the commonest symptoms complained by patients with COVID-19. Although chemosensory function has been reported improved in over 60% of COVID-19 patients in a short time after acute infection, it may last as a major symptom for patients with long COVID-19. This narrative review discussed current literatures on OD and GD in long COVID-19 including the prevalence, risk factors, possible mechanisms, and potential therapies.

RECENT FINDINGS

Although the prevalence of OD and GD has declined continuously after acute COVID-19, a considerable number of patients had persistent chemosensory disorders 3 months to 2 years after symptom onset. Female gender, initial severity of dysfunction, nasal congestion, emotional distress and depression, and SARS-CoV-2 variants have been identified as risk factors for persistent OD and GD in long COVID-19. The pathogenesis of OD and GD in long COVID-19 remains unknown, but may be analogous to the persistent OD and GD post common respiratory viral infection. Corticosteroids and olfactory training might be a potential choice regarding the treatment of lasting OD and GD after SARS-CoV-2 infection; however, more studies are needed to prove it. OD and GD are common long-term consequences of COVID-19 and influenced by gender, initial severity of dysfunction, emotional distress and depression, and SARS-CoV-2 variants. More studies are needed to illustrate their pathogenesis and to establish therapeutic strategies.

Dysphagia, dysphonia and olfactory disease: a map of Cochrane evidence relevant to rehabilitation for people with post COVID-19 condition

INTRODUCTION

Currently, no evidence exists on specific treatments for post COVID-19 condition (PCC). However, rehabilitation interventions that proved effective for similar symptoms in other health conditions could be applied to people with PCC. With this overview of systematic reviews with mapping, we aimed to describe the Cochrane evidence on rehabilitation interventions proposed for dysphagia, dysphonia and olfactory dysfunction in different health conditions that can be relevant for PCC.

EVIDENCE ACQUISITION

We searched the last five years' Cochrane Systematic Review (CSRs) using the terms "dysphagia," "swallowing disorder," "dysphonia," "voice disorder," "olfactory dysfunction," "smell changes" and "rehabilitation" in the Cochrane Library. We extracted and summarized the available evidence using a map. We grouped the included CSRs for health conditions and interventions, indicating the effect and the quality of evidence.

EVIDENCE SYNTHESIS

We found 170 CSRs published between 2016 and 2021 and 1 was included. It provided data on dysphagia in acute and subacute stroke. Interventions included were acupuncture, neuromuscular electrical stimulation, transcranial magnetic stimulation and behavioral interventions, and swallowing therapy, with very low- to moderate-quality evidence. We did not find any CSR on dysphonia and olfactory disease.

CONCLUSIONS

These results are the first step of indirect evidence able to generate helpful hypotheses for clinical practice and future research. They served as the basis for the three recommendations on treatments for these PCC symptoms published in the current WHO Guidelines for clinical practice.

Topical Administration of Mometasone Is Not Helpful in Post-COVID-19 Olfactory Dysfunction

Persistent olfactory dysfunction is a major concern post-COVID-19, affecting up to 5% of all patients. Different therapeutic options, including mometasone nasal spray, have been recommended, only some of which have been validated for post-COVID-19 olfactory dysfunction. In this study we psychophysically assessed the effect of intranasally applied mometasone furoate on the recovery of olfaction. The spray was applied with a long applicator so that the olfactory cleft could be reached effectively. After olfactory dysfunction had been confirmed psychophysically using Sniffin’ Sticks, patients were randomly assigned to two different treatment arms: the study group (n = 40) underwent olfactory training and intranasal administration of mometasone furoate twice daily, whereas the control group (n = 46) performed olfactory training only. After a study duration of three months, psychophysical testing of olfaction was repeated using Sniffin’ Sticks. We found no benefit of an additional topical administration of mometasone furoate compared to olfactory training alone. These results psychophysically confirm two previous studies which were based on patients’ subjective self-ratings. Our findings are in contrast to current recommendations for the management of olfactory dysfunction post-COVID-19, which might have to be adapted accordingly.

Assessment of Smell and Taste Disturbances among COVID-19 Convalescent Patients: A Cross-Sectional Study in Armenia

Background and Objectives: Neurological manifestations of Coronavirus Disease 2019 (COVID-19) such as olfactory and gustatory disturbance have been reported among convalescent COVID-19 patients. However, scientific data on the prevalence of smell and taste disturbance are lacking. Therefore, we present findings on the degree of smell and taste disturbances among the Armenian population. Methods: Study participants were randomly recruited and then categorized into two groups based on their course of the disease. A cross-sectional study was performed to assess participants’ sensitivity to smell triggered by the olfactory and the trigeminal nerves; their ability to differentiate between various odors; and to evaluate their gustatory perception. Results: The smell test revealed that the degree of olfactory nerve disturbance was different by 30.7% in those participants of the early group as compared to those of the late group, and the degree of trigeminal nerve disturbance was different by 71.3% in the early group as compared to the late group. A variation of the differentiating ability among the participants of the early and late groups was detected. Gustatory disturbances for all flavors were also found to be different in both the groups. A moderate positive correlation (0.51) was found between the overall sensitivity of smell and the ability to differentiate between various odors as cumulatively stimulated by both the olfactory and trigeminal nerves. Also, a moderate positive correlation (0.33) was found between headache and smell sensitivity through the olfactory nerve and a high negative correlation (−0.71) was found between headache and smell sensitivity through the trigeminal nerve. Conclusion: Pathological changes in the olfactory and trigeminal perceptive abilities caused disturbances in smell sensation, with the trigeminal nerve being more affected. The capacity to differentiate fragrances did not improve with time and the disturbance severity of bitter taste perception was higher among the study participants.

Development of restrictive eating disorders in children and adolescents with long-COVID-associated smell and taste dysfunction

BACKGROUND

Absent or abnormal senses of smell and taste have been frequently reported during both acute and long COVID in adult patients. In contrast, pediatric patients who test positive for SARS-CoV-2 are often asymptomatic and the loss of smell and/or taste has been infrequently reported. After observing several young patients with COVID-associated anosmia and ageusia at our clinic, we decided to investigate the incidence of subsequent eating disorders in these patients and in SARS-CoV-2 positive patients who did not experience anosmia and ageusia during the same period.

MATERIAL AND METHODS

A single-site retrospective cohort study of 84 pediatric patients with suspected long COVID who were treated in the Pediatric Infectious Diseases Outpatient Clinic at the University Hospital Essen were evaluated for persistent symptoms of COVID-19. Smell and taste dysfunction as well as eating behaviors were among the signs and symptoms analyzed in this study.

RESULTS

24 out of 84 children and adolescents described smell and taste dysfunction after confirmed or suspected SARS-CoV-2 infections. A large number of these patients (6 out of 24) demonstrated increased fixation on their eating behavior post-COVID and over time these patients developed anorexia nervosa.

DISCUSSION/CONCLUSION

In this study we saw a possible association of long-lasting post-COVID smell and taste dysfunction with subsequent development of eating disorders. This observation is worrisome and merits further investigation by healthcare providers at multiple clinical sites.