Olfactory threshold after nasal allergen challenge

Clinical factors influencing olfactory performance in patients with persistent COVID-19 smell loss longer than 1 year

Objectives

Factors affecting persistence of COVID-19-related olfactory dysfunction (OD) remain partially unknown. We aim to evaluate the clinical factors which could influence olfactory performance in patients with persistent COVID-19-related smell loss.

Methods

A retrospective analysis of 100 patients with persistent COVID-19-related OD was performed between October 2020 and December 2022 at a single-center long-COVID smell clinic. All subjects underwent smell assessment using Sniffin' Sticks (S'S) extended test, nasal endoscopy, nasal airflow evaluation (peak nasal inspiratory flow [PNIF]), allergy test (skin prick test [SPT]) for common aeroallergens, MRI of the head and patient-reported outcome measures (PROMs-VAS, SF-36, Short QOD-NS, SNOT-22). Based on S'S score, subjects were divided into normosmics (TDI ≥ 30.75) and dysosmics (TDI < 30.75).

Results

The median age was 42 years and the median length of patient-reported OD was 1.4 years. 20 patients (20.0%) were normosmic at the time of S'S assessment. Dysosmic patients were found to have significantly lower scores at the SF-36 health domains for energy/fatigue (p = .0004) and emotional wellbeing (p = .04) when compared to normosmics. A moderate correlation (r = .45-.59) between S'S scores and some PROMs was also demonstrated. At the multivariate analysis higher PNIF scores positively influenced odor threshold (p = .001) while positivity to SPT negatively influenced odor identification (p = .04).

Conclusions

Impairment of nasal airflow and sensitivity to aeroallergens can negatively affect olfactory performance in COVID-19-related OD. Long-COVID smell loss deeply affects QoL although recovery of olfaction can bring it back to a normal range.

Level of Evidence

IV.

Olfaction in patients with allergic rhinitis: an indicator of successful MP-AzeFlu therapy

BACKGROUND

The purpose of this study was to investigate the effect of MP-AzeFlu on olfaction and the interaction between severity of allergic rhinitis and olfactory improvement after therapy.

METHODS

A prospective, multicenter, observational study was performed on 47 patients with persistent allergic rhinitis. Duration and severity of allergic rhinitis was diagnosed and classified using the modified Allergic Rhinitis and its Impact on Asthma (ARIA) criteria and the proof of allergen sensitization from positive skin-prick tests, specific immonoglobulin E (IgE) in serum, and nasal provocation response. Patients were treated with MP-AzeFlu (1 spray/nostril twice daily) over 3 months. Olfactory function was assessed at baseline and at 1 and 3 months of therapy using the "Sniffin' Sticks" test. In addition, a nasal symptom score was recorded on a visual analog scale (VAS) at each given time-point.

RESULTS

MP-AzeFlu was found to be associated with a significant improvement in TDI score, from 23.7 at baseline to 34.2 at 1 month (p < 0.001) and 37.1 at 3 months (p < 0.001) of treatment. Furthermore, a highly significant improvement of symptoms over time (p < 0.001; VAS at baseline: 84.3; 1 month: 32.4; 3 months: 26.2) could be demonstrated. Most importantly, there was a highly significant interaction between the severity of allergic rhinitis and olfactory function (p < 0.001) and VAS (p < 0.001).

CONCLUSION

MP-AzeFlu is associated with olfactory improvement in persistent allergic rhinitis patients. Further, the modified ARIA severity classification is an indicator of patients' olfactory function. Moreover, assessment of olfaction seems to be a reliable indicator of the clinical success of antiallergic/antiinflammatory therapy.

Olfaction in allergic rhinitis: A systematic review

Olfactory dysfunction is a key symptom in patients with allergic rhinitis (AR). Despite the implications for quality of life, relatively few articles have tested olfactory function in their investigations. The current systematic review aimed to investigate the following 2 questions: (1) What does AR do to human olfaction? (2) How effective is the treatment of AR in restoring the sense of smell? A comprehensive literature search was performed, and human studies of any design were included. A total of 420 articles were identified, and 36 articles were considered relevant. Data indicate that the frequency of olfactory dysfunction increases with the duration of the disorder, and most studies report a frequency in the range of 20% to 40%. Although olfactory dysfunction does not appear to be very severe in patients with AR, its presence seems to increase with the severity of the disease. There is very limited evidence that antihistamines improve olfactory function. In addition, there is limited evidence that topical steroids improve the sense of smell, especially in patients with seasonal AR. This is also the case for specific immunotherapy. However, many questions remain unanswered because randomized controlled trials are infrequent and only a few studies rely on quantitative measurement of olfactory function.

Psychophysical effects of nasal and oral inflammation

Olfactory disorders are common in "nasal inflammation" even though the term is comprehensive and subsumes different kinds of entities which have to be differentiated. The most common cause of olfactory disorders are sinonasal disorders, which are defined as secondary smell disorders caused by diseases/pathologies in the nose/paranasal sinuses. According to the literature, sinonasal disorders represent--depending on the examined population-up to 72% of all olfactory disorders. In general, noninflammatory and inflammatory disorders are differentiated. Inflammatory disorders can be further classified into infectious or noninfectious disorders, both forms in which olfactory disorders can be present. For the clinician examining patients, the exact classification of the olfactory disorder is mandatory in order to choose appropriate treatment and counseling. Among the most common inflammatory disorders are acute rhinitis, allergic rhinitis, post-upper respiratory tract infection and chronic rhinosinusitis, which are discussed in detail. In contrast to nasal inflammation, only little is known about oral inflammation and its psychophysical effects on taste function. Taste disorders following oral inflammation are briefly discussed.

Persistent allergic rhinitis has a moderate impact on the sense of smell, depending on both nasal congestion and inflammation

OBJECTIVES/HYPOTHESIS

A degree of smell disturbance has been found in seasonal and perennial allergic rhinitis, but alterations in olfaction in patients with persistent allergic rhinitis (PER) have not yet been evaluated. The aims of the study were to evaluate the impact of PER on the sense of smell, and to characterize this impact based on self-reported hyposmia (SRH) and PER severity.

STUDY DESIGN/METHODS

A prospective controlled study was performed on 49 consecutive patients with PER. PER patients were subclassified depending on severity and the presence of SRH. Olfactory function was evaluated by the Barcelona Smell Test-24 (BAST-24) olfactometry for smell detection, identification, and forced choice for first and fifth cranial nerve (CN) dependent odors in comparison to a group of 60 healthy volunteers. In patients with SRH, obstruction was evaluated by peak nasal inspiratory flow (PNIF) and acoustic rhinometry; and nasal inflammation was evaluated by nasal nitric oxide (nNO).

RESULTS

Most patients with PER (67%) presented SRH. Moderate/severe PER (84.8%) predominated among patients with SRH, while mild PER (75%) predominated among patients without SRH. Smell detection, identification, and forced choice tests were significantly worse in PER patients (P < .05) than in healthy controls for the odors related to the first and fifth CN. Among subgroups, patients with moderate/severe PER and/or with SRH presented a significant reduction in smell detection (P < .05) compared to healthy controls. Nasal NO correlated (R: 0.4; P < .05) with loss of smell.

CONCLUSIONS

Patients with PER have a moderate loss of smell (BAST-24) with a higher impairment in those with self-reported hyposmia and moderate-to-severe PER. These results suggest that the sense of smell should be further investigated in all patients with allergic rhinitis, both in a clinical setting and in clinical trials.

[Olfactory disorders]

Smell and taste problems are of major importance to those who suffer from olfactory disorders. The inability to determine the presence of odors in the home and the markedly reduced capacity or incapacity to appreciate food flavors are key reasons given for limited social interaction. Patients experiencing distorted smells and tastes may avoid food, which results in weight loss and possible malnutrition. We present an overview of smell disorders, based on physiological considerations, with specific attention to clinical characteristics of conditions most commonly causing smell disorders.

Ocular, airway, and dermal symptoms related to building dampness and odors in dwellings

The authors examined the relationship between symptoms of Sick Building Syndrome and reports of building dampness and odors. Two hundred thirty-one multifamily buildings built prior to 1961 in Stockholm, Sweden, contained a total of 4,815 dwellings. The authors selected these buildings for study by stratified random sampling. Occupants answered a postal questionnaire that assessed weekly symptoms, personal factors, population density in each apartment, water leakage in the preceding 5 yr, different types of odors, and signs of high indoor air humidity. The response rate was 77%. Independent information on building characteristics was gathered from the building owners and the central building register in Stockholm. Multiple logistic-regression analysis was applied and odds ratios were calculated, with adjustments for age, gender, current smoking, hay fever, population density, type of ventilation, and ownership of the building. In total, 22% reported at least 1 sign of dampness, and 32% reported odor in the dwelling. Condensation on windows, high air humidity in the bathroom, moldy odor, and water leakage were reported from 6.8%, 8.8%, 5.7%, and 13% of the dwellings, respectively. A combination of odor and signs of high humidity was related to an increased occurrence of all symptoms (odds ratios = 2.2-3.6). Similar findings were observed for a combination of odors and a history of water leakage in the past 5 yr (odds ratios = 1.2-4.4). Symptoms increased with the number of signs of dampness. The study indicated that dampness in dwellings, with emissions of odorous compounds, are associated with an increase in symptoms consistent with Sick Building Syndrome.

Olfaction and its alteration by nasal obstruction, rhinitis, and rhinosinusitis

The sense of smell has been largely ignored by otorhinolaryngologists, even though 1) its medical stewardship falls within their specialty's purview, 2) olfactory dysfunction is not uncommon in the general population, and 3) disorders of olfaction have significant quality of life, nutritional, and safety consequences. This report provides a succinct overview of the major intranasal neural systems present in humans (namely, cranial nerves O, I, and V, and the nonfunctional accessory [vomeronasal] organ system), along with a summary of notable findings resulting from the application of modern olfactory tests to patient populations, emphasizing diseases of the nose. Such tests have led to the discovery of significant influences of age, gender, smoking, toxic exposure, and genetics on the ability to smell. Within the field of otorhinolaryngology, they have revealed that 1) surgical and medical interventions in patients with rhinosinusitis do not, on average, lead to complete recovery of olfactory function, despite common beliefs to the contrary, and 2) associations are generally lacking between measures of airway patency and olfactory function in such cases. These findings have thrown into question the dogma that olfactory loss in rhinosinusitis is attributable primarily to blockage of airflow to the receptors and have led to histopathological studies demonstrating significant olfactory epithelial compromise in sinonasal syndromes.

A randomized controlled study evaluating medical treatment versus surgical treatment in addition to medical treatment of nasal polyposis

BACKGROUND

Controlled prospective studies are needed to determine whether surgical treatment in fact has an effect additive to that of medical treatment of nasal polyposis.

OBJECTIVE

We sought to compare the effect of medical treatment versus combined surgical and medical treatment on olfaction, polyp score, and symptoms in nasal polyposis.

METHODS

Thirty-two patients with nasal polyposis and symmetrical nasal airways were randomized to unilateral endoscopic sinus surgery after pretreatment with oral prednisolone for 10 days and local nasal budesonide bilaterally for 1 month. Postoperatively, patients were given local nasal steroids (budesonide). Patients were evaluated with nasal endoscopy, symptom scores, and olfactory thresholds. They were followed for 12 months.

RESULTS

The sense of smell was improved by the combination of local and oral steroids. Surgery had no additional effect. Symptom scores improved significantly with medical treatment alone, but surgery had additional beneficial effects on nasal obstruction and secretion. After surgery, the polyp score decreased significantly on the operated side but remained the same on the unoperated side. Twenty-five percent of the patients were willing to undergo an operation also on the unoperated side at the end of the study.

CONCLUSIONS

Medical treatment seems to be sufficient to treat most symptoms of nasal polyposis. When hyposmia is the primary symptom, no additional benefit seems to be gained from surgical treatment. If nasal obstruction is the main problem after steroid treatment, surgical treatment is indicated. Selection of those who will benefit from surgery should be based on the patient's symptoms and not on the examiner's polyp score.

Olfactory function in acute rhinitis

This study was performed to investigate the effects of the common cold on olfactory function, which was assessed using chemosensory event-related potentials (CSERP, in response to both olfactory [H2S] and trigeminal [CO2] stimuli) and psychophysical measures (intensity ratings, odor discrimination, butanol threshold); nasal volume was assessed by means of acoustic rhinometry. The investigation was performed in 36 subjects (18 women, 18 men). After onset of the rhinitis (day 0) measurements were performed on days 2, 4, 6 and 35. The cold produced a decrease of the volume of the anterior nasal cavity accompanied by an increase of mucus secretion, an increase of olfactory thresholds, a decrease of intensity ratings and a decrease of N1 CSERP amplitudes to olfactory and trigeminal stimuli. When mucus secretion of the contralateral nasal cavity was controlled with oxymetazoline, N1 amplitudes to olfactory stimuli were still affected by the cold as indicated by the significant increase of amplitudes as subjects recovered; this phenomenenon was not found for responses to trigeminal stimuli. This indicates that the common cold has a small effect on olfactory function which may be independent of nasal congestion.