Abstract
Olfactory loss has been identified as one of the common symptoms related to COVID-19 infection. Although olfactory loss is recognized, our understanding of both the extent of loss and time to olfactory recovery following infection is less well known. Similarly, knowledge of potential impactful patient factors and therapies that influence olfactory recovery is desirable but is not overtly clear in the literature. Our systematic review sought to fill this knowledge gap. We included studies that: involved either an observational or an interventional design that reported data on patients with olfactory dysfunction due to Reverse Transcription Polymerase Chain Reaction (RT-PCR) diagnosed COVID-19 infection; and reported data regarding olfactory recovery measured by an objective olfactory test, Likert scale and/or visual analog scale (VAS). The study methods were determined a priori and registered in PROSPERO (Registration Number CRD42020204354). An information specialist searched Medline, Embase, LitCovid and the Cochrane Register of Controlled Trials up to March 2021, and two reviewers were involved in all aspects of study selection and data collection. After screening 2788 citations, a total of 44 studies of assorted observational designs were included. Patients had undergone objective COVID-19 testing, and most were adult patients with mild to moderate COVID-19. Olfactory recovery was found to occur as early as 7 days, with most patients recovering olfaction within 30 days. Few studies included prolonged follow-up to 6 months or longer duration. Poor olfaction at initial presentation was associated with poor recovery rates. Only a small number of studies assessed olfactory retraining and steroid therapy. Additional trials are underway.
Highlights
MethodsStudies involving either an observational or interventional design were of interest
The spread of Coronavirus (COVID-19) infection was announced by the World Health Organization to be a pandemic on March 11th 2020 [1]
We identified variability amongst studies on type of measurement instrument adopted to assess olfactory function, the initial timing of assessment for olfactory dysfunction, the follow-up evaluation tools and intervals
Summary
Studies involving either an observational or interventional design were of interest. No restrictions related to follow-up duration were employed. We excluded all review articles, case reports, letters, editorials, commentaries, and abstracts. The primary outcome of interest was the extent of olfaction recovery following COVID-19 infection, using objective or subjective measures. A baseline measurement of olfactory loss at time of infection or at study intake was compared to subsequent measurements at follow up intervals. Olfactory loss could be reported as a continuous or categorical measurement (anosmia, hyposmia, normosmia). Our secondary outcomes of interest included time to olfactory recovery, patient prognostic factors (for occurrence and resolution of olfactory dysfunction), and interventional therapies used for olfactory recovery
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
