OLFACTORY TRAINING EFFICIENCY IN POST-COVID-19 PERSISTENT OLFACTORY DISORDERS (preprint)

ABSTRACT Background Persistent post-viral olfactory disorders (PPVOD) are widely reported after a COVID-19 and estimate to 30% one year after infection. Parosmias are the main qualitative dysosmia associated with olfaction recovery. No treatment is, to date, significantly efficient on PPVOD except olfactory training (OT). The main objective of this work was to evaluate OT efficiency on post-COVID-19 PPVOD. Methods Consecutive patients consulting to the ENT department with post-COVID-19 PPVOD were included after mainly clinical examination, the complete Sniffin’ Stick Test (TDI), the short version of the Questionnaire of olfactory disorders and the SF-36. Patients were trained to practice a self-olfactory training (professional manufactured olfactory training kit) twice a day for 6 months before coming back and undergo the same complete evaluation. Results Forty-three patients were included and performed 3,5 months of OT in average. There was a significant improvement in the mean TDI score increasing from 24,7 (±8,9) before the OT to 30,9 (±9,8) (p<0,001). Parosmias increased significantly from 8 (18,6%) to 27 (62.8%) (p<0,001). Based on normative data divided by sex and age, a significant increase in the number of normosmic participants was only found for the Threshold values (p<0,001). Specific and general olfaction-related quality of life improved after the OT. Conclusions OT seems to be efficient in post-COVID-19 PPVOD, probably on the peripheral regenerative part of the olfactory recovery. Future therapeutic strategies may focus on the central aspects of the post-COVID-19 PPVOD.

High prevalence of olfactory disorders 18 months after contracting COVID-19 (preprint)

Reduced olfactory function is the symptom with the highest prevalence in COVID-19 with nearly 70% of individuals with COVID-19 experiencing partial or total loss of their sense of smell at some point during the disease. Recent reports suggest that more than 7 months after recovering from COVID-19, a large proportion of these individuals still have olfactory dysfunction of some form. To establish the prevalence of olfactory dysfunction 18 months and beyond, we tested 100 individuals with established COVID-19 in the first wave of the pandemic using psychophysical full-scale testing of smell and taste functions as well as assessments of parosmia. Participants were recruited from an ongoing study, comprising healthcare workers at a hospital in Stockholm, Sweden, that are regularly tested for SARS-CoV-2 IgG antibodies since the start of the pandemic in Sweden. To assess potential skewed recruitment of individuals with prior olfactory dysfunction and assess normal rate of dysfunctions in the used population, 44 SARS-CoV-2 IgG naïve individuals were also tested as a control group. One and a half year after COVID-19, more than one third of individuals recovered from COVID-19 demonstrated a clinical reduction in their sense of smell. Critically, nearly half of COVID-19-recovered individuals’ complaint about parosmia. Prevalence of gustatory dysfunction was, however, low (3%). In summary, a full 65% of individuals recovered from COVID-19 experience olfactory dysfunction of some form 18 months later. Given the amount of time since initial insult to the olfactory system, it is likely that these olfactory problems are permanent.

An analysis of patients’ perspectives on qualitative olfactory dysfunction using social media (preprint)

SUMMARY Background The impact of qualitative olfactory disorders is underestimated. Parosmia is the triggered perception of distorted odours whereas phantosmia is the perception of odours in the absence of a trigger. Both can arise from post-infectious anosmia and have increased substantially since the outbreak of COVID-19. Methodology/Principal Thematic analysis of a social media support group for parosmia and phantosmia was used to articulate the perspectives and concerns of those affected by these debilitating olfactory disorders. Results A novel symptom (olfactory perseveration) was identified where a triggered, identifiable, and usually unpleasant olfactory percept persisted in the absence of an ongoing stimulus. Fluctuations in intensity and duration of perseveration, parosmia and phantosmia were observed. Coffee, meat, onion, and toothpaste were identified as common triggers of these disorders, but people struggled to describe the distortions, using words associated with disgust and revulsion. Common strategies to avoid triggers may result in a diet lacking in both nutrition and reward. The emotional aspect of living with qualitative olfactory dysfunction was evident and highlighted the detrimental impact on mental health. Conclusions The data acquired can inform rehabilitation strategies and drive our ongoing research into understanding the molecular triggers associated with parosmia, and research into patient benefit.

Diagnostic Value of Reported and Clinically Tested Olfactory Disorders in a Population Screened for COVID-19 (preprint)

Background: Recent studies suggested that olfactory and gustatory disorders were highly correlated with COVID-19, but olfaction was evaluated solely on reported symptoms, after COVID-19 diagnosis, or in combined mild and severe COVID-19. We investigated the diagnostic value of patient-reported and clinically tested chemosensory disorders in patients attending a COVID-19 screening center. Methods: In this prospective diagnostic test study, we consecutively included healthcare workers and outpatients with symptoms or close index case contact. Prior to nasopharyngeal swabbing for SARS-CoV-2 RT-PCR, participants were interviewed for symptoms, then underwent the Clinical Olfactory Dysfunction Assessment (CODA), which is a standardized test developed for a simple and fast olfactory evaluation. Participants identified and rated the intensity of three scents, summing to a score ranging from zero to six. Findings: Among 809 participants, 58 (7·2%) tested positive for SARS-CoV-2. Patient-reported chemosensory disorders prevalence was 34·5% in COVID-19 confirmed cases ( vs 3·9%, p<0·001). Olfactory disorders, either reported or clinically tested (CODA≤3), yielded similar sensitivities of 0·31 (95% CI 0·20–0·45) and 0·34 (0·22–0·48), and specificities of 0·97 (0·96–0·98) and 0·98 (0·96–0·99) respectively for COVID-19 diagnosis. Concordance was high between reported and clinically tested olfactory disorders, AC1=0·95 (95% CI 0·93–0·97). 18 of 19 participants with both reported olfactory disorders and CODA≤3 had COVID-19. Interpretation: Olfactory disorders are highly specific but poorly sensitive for COVID-19. Patients with olfactory disorders are prevalent in and suggestive of COVID-19, particularly if clinical testing confirms anamnesis. However, normal olfaction is common in COVID-19.Trial Registration: registered on ClinicalTrials.gov (NCT04407494)Funding Statement: This research did not receive any funding.Declaration of Interests: All authors declare no competing interests.Ethics Approval Statement: This study was a prospective monocentric study, approved by the Institutional Review Board (IRBMPT-2020_03_202000424).