Olfactory Training in Post-COVID-19 Persistent Olfactory Disorders: Value Normalization for Threshold but Not Identification

  1. Clair Vandersteen
  2. Magali Payne
  3. Louise-Émilie Dumas
  4. Élisa Cancian
  5. Alexandra Plonka
  6. Grégoire D’Andréa
  7. David Chirio
  8. Élisa Demonchy
  9. Karine Risso
  10. Florence Askenazy-Gittard
  11. Charles Savoldelli
  12. Nicolas Guevara
  13. Philippe Robert
  14. Laurent Castillo
  15. Valeria Manera
  16. Auriane Gros

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Abstract

(1) Background: Persistent post-viral olfactory disorders (PPVOD) are estimated at 30% of patients one year after COVID-19 infection. No treatment is, to date, significantly effective on PPVOD with the exception of olfactory training (OT). The main objective of this work was to evaluate OT efficiency on post-COVID-19 PPVOD. (2) Methods: Consecutive patients consulting to the ENT department with post-COVID-19 PPVOD were included after completing 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 with a dedicated olfactory training kit twice a day for 6 months before returning to undergo the same assessments. (3) Results: Forty-three patients were included and performed 3.5 months of OT in average. We observed a significant TDI score improvement, increasing from 24.7 (±8.9) before the OT to 30.9 (±9.8) (p < 0.001). Based on normative data, a significant increase in the number of normosmic participants was observed only for the threshold values (p < 0.001). Specific and general olfaction-related quality of life improved after the OT. (4) Conclusions: Olfactory function appeared to improve only in peripheral aspects of post-COVID-19 PPVOD after OT. Future controlled studies must be performed to confirm the OT role and justify new therapeutic strategies that may focus on the central aspects of post-COVID-19 PPVOD.

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  1. Version published to 10.3390/jcm11123275
  2. ScreenIT

    SciScore for 10.1101/2022.02.27.22271572: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsIRB: Population: The study was approved by the institutional review board of the Nice University Hospital
    Sex as a biological variablenot detected.
    RandomizationIt involved 6-months olfactory training with daily odors exposure, twice a day (2 sessions), with 2 different random odors of the kit, the morning and the evening (four different odors per day).
    BlindingPatients were well-informed, once all odors used at least one time, to try to recognize by blindly sniffing them.
    Power Analysisnot detected.
    Cell Line AuthenticationAuthentication: Objective olfactory dysfunction: Olfactory function was assessed using Sniffin’ Sticks test, a validated psychophysical test that included a phenyl-ethyl alcohol (PEA) odor Threshold detection (T), an odor Discrimination (D) and an odor Identification (I) test.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    This study had however several limitations. We did not use a control group as it’s often the case in OT study because it’s ethically difficult not to treat a patient, and technically impossible or quite difficult to use placebo odors. Concerning TDI results, we can wonder if spontaneous recovery could have produced the same results. It’s hard to answer to that question formally as, with similar complete (T,D,I) SST evaluations, there are only a few studies reporting spontaneous post-COVID-19 olfactory recovery(47,48), and even less reporting it after OT(29). Iannuzzi et al.(49) found a significant T progression evaluated after 2 months of spontaneous olfactory recovery, which may correspond to early olfactory neurons and sustentacular regeneration occurring around 2 to 4 weeks in such inflammatory environment(50). Compared to D and I, we previously reported(8) that T was the most decreased olfaction subdimension measured in a cohort of patients with near 6 months post-COVID-19 PPVOD, confirming what many authors found in similar patients after 4(48) or 6(47) months of spontaneous recovery with a tiny or non-significant increasing of T. There is, to date, no potential explanation that could validate a spontaneous T increasing after 6 months of persistent post-COVID-19 olfactory loss. Spontaneous recovery occurred mainly in the first month and does not change afterward. Another limit is the absence of psychophysical taste evaluation even if, after 6 months, almost all patients ...

    Results from TrialIdentifier: We found the following clinical trial numbers in your paper:

    IdentifierStatusTitle
    NCT04799977RecruitingCOVID-19: Post-covid Olfactory Disorders Assessment

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

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  3. Version published to 10.1101/2022.02.27.22271572v1 on medRxiv