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High prevalence of long-term olfactory dysfunction confirmed by olfactory testing after a community COVID-19 outbreak

Purpose

The prevalence of long-term olfactory and gustatory dysfunction in participants suffering from sudden chemosensory loss due to coronavirus disease 2019 (COVID-19) is unknown. Furthermore, evaluations of the reliability of participants’ self-reporting of olfactory function (SOF) and gustatory function (SGF) using extended objective psychophysical testing are missing.

Methods

In this population-based cohort study in a PCR-tested community in Thuringia, Germany, olfactory function was extensively examined 4 months after a COVID-19 outbreak using the “Sniffin Sticks” test battery to determine the TDI_a score, i.e., the sum of results obtained for threshold, discrimination, and identification scores averaged for both nasal sides. Gustatory function was assessed using the three-drop test resulting in the gustatory composite score (CS_g). The data were compared with SOF and SGF.

Results

Of 43 adult convalescents (median age: 68 years; 58% female) after SARS-CoV‑2 infection, 18 participants (42%) had olfactory complaints due to SOF, one participant (2%) complained of taste disturbance due to SGF. The TDI_a was 22.0 ± 5.9. Normosmia, hyposmia, and anosmia were seen in 17, 18, and eight participants, respectively. TDI_a correlated with SOF (r_s = −0.434, p = 0.004); CS_g was 23.5 ± 2.7. Normogeusia and hypogeusia were objectified in 39 and four participants, respectively. The prevalence of long-term olfactory dysfunction and gustatory dysfunction in the study group was 60.5 and 9.3%, respectively.

Conclusion

The SOF was reliable, especially for participants who felt a sudden chemosensory dysfunction during the outbreak. At 4 months after SARS-CoV‑2 infection, a high proportion of participants were dysosmic, whereas nearly all of them had normal taste function.

The Influence of Cognitive Parameters on Olfactory Assessment in Healthy Children and Adolescents

Olfactory threshold and odor identification tests are frequently used for assessment of olfactory function in children and adolescents. Whether olfactory test results are influenced by cognitive parameters or sex in children and adolescents is largely unknown. The aim of this study was to investigate the influence of cognition, age and sex on "Sniffin' Sticks" olfactory threshold and "U-Sniff" odor identification performance in a pediatric population. A total of 200 participants between age 6 and 17 years were included. Olfactory function (olfactory threshold and odor identification) was assessed using the "Sniffin' Sticks." In addition, age appropriate cognitive testing was applied. The results of this study indicate that odor identification test performance is positively correlated with age (r = 0.31) and verbal abilities of children (r = 0.24). Olfactory threshold results are only marginally influenced by age (r = 0.18) and are not associated with cognitive test performance. Olfactory assessment using olfactory threshold and "U-Sniff" odor identification testing is suitable for children and adolescents when considering age in the interpretation of test results.

Consequences of undetected olfactory loss for human chemosensory communication and well-being

Olfactory perception has implications for human chemosensory communication and in a broader context, it affects well-being. However, most of the studies investigating the consequences of olfactory loss have recruited patients who have already been categorized as having a dysfunctional sense of smell and sought help in an ENT clinic. We revisit these findings by distinguishing subjects with olfactory impairment from a group of subjects who all declared a normal sense of smell when enrolling for this study. In the initial sample of 203 individuals, we found 59 to have impaired olfaction and four with marginal olfactory performance, not useful in daily life. Interestingly, we found a significant between-group difference in cognitive functioning, further supporting the notion of the relationship between cognition and olfactory performance. However, their chemosensory communication and well-being appeared not to be different from subjects with normosmia. Impaired olfactory function certainly has a severe impact on daily life but more so in individuals who are bothered with it and decide to seek treatment. The limited-to-no olfactory perception in the fraction of subjects who neither complain about it nor seek help in ENT clinics does not seem to have a major effect on their social, cognitive, emotional and health functioning. This article is part of the Theo Murphy meeting issue 'Olfactory communication in humans'.

Computed Tomography Scans in the Evaluation of Patients with Olfactory Dysfunction

Background

The necessity of computed tomography (CT) scans of the olfactory cleft and the sinuses in patients presenting with olfactory dysfunction is a matter of debate. This study aimed to investigate the significance of CT scans for the diagnosis of olfactory loss and for therapeutic decisions.

Methods

This retrospective study included 137 consecutive patients presenting with the main complaint of olfactory loss. Standardized history; ear, nose, and throat examination; and olfactory tests were administered. In addition, a CT scan of the nasal sinuses was obtained. The assumed diagnosis (sinonasal disease [SND] or non-SND) was compared with the diagnosis when additionally considering results from the CT scan.

Results

CT scans suggested SND in 7/101 patients without clinical evidence of its presence. In 12/36 patients with suspected SND-related olfactory loss, no signs of SND were detected in CT scans.

Conclusion

CT scans are useful to diagnose conductive/inflammatory olfactory loss in patients suspected of non-SND, which may then justify a course with systemic steroids. Alternatively, considering low costs and rare side effects of a short course with steroids in selected patients, CT scans appear to be of clinical significance only when surgical treatment is contemplated or where the use of systemic corticosteroids is not possible.

Olfactory threshold and odor discrimination ability in children - evaluation of a modified "Sniffin' Sticks" test

The clinical diagnostics of olfactory dysfunction in children turns out to be challenging due to low attention span, insufficient linguistic development and lack of odor experiences. Several smell tests have been developed for adults. Most of these examinations take a relatively long time and require a high level of concentration. Therefore, the aim of the current study was to evaluate an odor discrimination and olfactory threshold test using the frequently used “Sniffin’ Sticks” in children and adolescents in a simplified two-alternative-forced-choice version (2AFC) and compare it to the original three-alternative-forced-choice test (3AFC). One-hundred-twenty-one healthy participants aged between 5 and 17 years took part in this study. Within each of the two sessions participants underwent olfactory testing using the modified 2AFC as well as the standard 3AFC method. A better test-retest reliability was achieved using the original 3AFC method compared to the modified 2AFC. This was true for the odor discrimination as well as the olfactory threshold. Age had a significant influence on both tests, which should be considered when testing young children. We discuss these findings with relation to the existing norms and recommend using the 3AFC version due to a better test-retest reliability to measure olfactory function in children.

Topical beclomethasone in the therapy of smelling disorders-a new application technique

Systemic corticosteroid is the first-line-treatment for olfactory dysfunction of sinonasal origin but is afflicted with many side-effects. Topic corticosteroid does not reach the same efficacy but has a remarkable safety profile. In this trial we investigated the efficacy of topic therapy with beclomethasone (BDP) -spray. The drug was applied precisely to the olfactory cleft by a special spraying top-part. In addition we determined extinction and volume of a gelaspon sponge placed in the olfactory cleft to show the difference of the topical spray application. 18 patients with anosmia or hyposmia of different genesis and duration applied BDP-spray twice daily for four weeks. The olfactory function was determined using the TDI score ('Sniffin'-Sticks test battery'). Factors correlated with therapy efficacy were assessed. The median TDI score increased from 13.5 (0-25) at the beginning to 18.5 (1-26) after therapy of four weeks (P = 0.005). The extinction and volume in the moistened sponge was more than two times greater with the top-part than without. The direct application of BDP-spray to the olfactory cleft attained superior therapeutic effects than a usual applied mometasone spray, but did not perform as good as systemic corticosteroid treatment.

[Studies of the olfactory epithelium in anosmic patients after head trauma]

BACKGROUND

An additional diagnostic option for olfactory dysfunction is the study of the olfactory epithelium.

METHODS

Biopsies of the olfactory epithelium were performed under local anaesthesia on five patients with a history of head trauma with anosmic results in the Sniffin' Sticks test. The biopsy of a normosmic patient served as a control. Immunochemistry of frozen sections and explant culture studies were made, investigating ability to attach to the culture plate and the outgrowth of neuronal cells after growth-factor stimulation.

RESULTS

The biopsies were carried out without any complications. All biopsies were positive for neurofilament, a marker for immature neurons. Substantial differences in the explants' ability to attach to the culture plate occurred, with a rate of between 25% and 100%. The control showed 67%. After stimulation with growth factors (FGF(2)), the cultures with more attached cells showed neuronal differentiation with the appearance of bipolar cells.

CONCLUSIONS

The biopsy of the human olfactory epithelium is a minimally invasive procedure which can provide further information on specific changes and possible regenerative ability. Further studies with larger numbers of patients with different causes of an impaired sense of smell are needed to determine specific changes.