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Randomized Controlled Trial
. 2025 Apr;15(4):420-427.
doi: 10.1002/alr.23505. Epub 2024 Dec 30.

Long-term Outcomes of PRP Injections for Post-viral Olfactory Loss: A Prospective Cohort Study

Maxime Fieux  1   2 , Bruna R Castro  1 , Sophie S Jang  3 , Carol H Yan  3 , Zara M Patel  1
Affiliations
Randomized Controlled Trial

Long-term Outcomes of PRP Injections for Post-viral Olfactory Loss: A Prospective Cohort Study

Maxime Fieux et al. Int Forum Allergy Rhinol. 2025 Apr.

Abstract

Background: Platelet-rich plasma (PRP) injections have previously been shown to benefit coronavirus disease 2019 (COVID-19)-induced smell loss. It is unknown if that benefit is stable over time. The aim of this study was to assess outcomes at 1-year post-intervention.

Methods: Prospective cohort study. Sixteen patients (10 PRP and six placebo) from the original PRP randomized placebo-controlled clinical trial, and a further 16 patients from smell clinic who were a year out from initial treatment (six PRP patients and 10 non-PRP) were enrolled. University of Pennsylvania Smell Identification Tests (UPSITs) and visual analog scale (VAS) subjective scores were compared to initial scores.

Results: There was no difference between groups with respect to age, gender, race, duration of smell loss prior to intervention, smoking or diabetes status, Charlson comorbidity index, presence of phantosmia or parosmia, or baseline UPSIT score. The PRP group had a significantly higher change in UPSIT score at 1 year (p = 0.001), a higher number of patients who met the minimal clinically important difference for the UPSIT (87.5% vs. 31.2%, p = 0.004), and a significantly greater change in VAS at 1 year (p = 0.001), compared to those who did not receive injections. On multivariate logistic regression analysis, no factors appeared to have a significant effect on these findings.

Conclusion: PRP injections into the olfactory cleft now have long-term data suggesting benefit in both subjective and psychophysical measures of smell, and improvements in both realms at 1 year are significantly higher than in those who do not receive the injections.

Keywords: anosmia; hyposmia; long‐term effect; olfaction disorders; platelet‐rich plasma; smell disorders; smell loss.

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Conflict of interest statement

Conflicts of Interest

M.F. is a consultant for Sanofi, GlaxoSmithKline, and AstraZeneca. Z.M.P. is a consultant/advisory board for Medtronic, Dianosic, Optinose, Mediflix, ConsumerMedical, and has equity in Olfera Therapeutics, SoundHealth, and Wyndly. The remaining authors declare they have no conflicts of interest.

Figures

FIGURE 1 |
FIGURE 1 |
Schematic representation of the steps and platelet-rich plasma (PRP) preparation. Detailed representation of steps from presentation with olfactory dysfunction through three bi-weekly injections and to the final evaluation at 1 year. Abbreviations: UPSIT, University of Pennsylvania Smell Test; VAS, visual analog scale.
FIGURE 2 |
FIGURE 2 |
Olfactory outcomes based on University of Pennsylvania Smell Test (UPSIT) (A) and visual analog scale of subjective smelling ability (VAS olfaction) (B). (A) Change in UPSIT between baseline and 1 year. (B) Change in VAS olfaction between baseline and 1 year.
See this image and copyright information in PMC

References

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