Effectiveness and safety of PRP on persistent olfactory dysfunction related to COVID-19

Abstract

Introduction Olfactory dysfunction (OD) is a well know symptom of coronavirus disease 2019 (COVID-19), accounting for 48 to 85% of patients. In 1 to 10% of cases, patients develop a chronic olfactory dysfunction (COD), lasting more than 6 months. Recently, platelet-rich plasma (PRP) was used in patients with non-COVID-19 COD and authors reported encouraging results. Methods In the present study, we investigated the usefulness and safety of PRP injection in 56 patients with COVID-19 COD by the Sniffing Stick test (TDI score) and a linker-scale from 0 (none) to 3 (strong) and we compare the result to a control group. Results At 1 month post-PRP injection, the mean TDI scores significantly improved by 6.7 points in the PRP group ( p < 0,001), the mean self-assessment of improvement in smell function was 1.8 (mild-to-moderate) in the PRP group, which was significantly higher than the score (0.3) in the control group ( p < 0,001). Conclusion Our results showed that PRP in the olfactory cleft can increase the olfactory threshold 1 month after the injection. Moreover, our results suggest that timing of treatment may be an important factor and that PRP is a safe treatment, because no adverse effects were reported throughout the study. Trial registration number: NCT05226546.

Use of platelet‐rich plasma for COVID‐19–related olfactory loss: a randomized controlled trial

“… 31 Steffens et al utilized our protocol and injection volume in their recent PRP study. 22 In this study, our PRP preparation technique resulted in an average 5.9‐fold increase in platelet concentration compared with whole blood (Figure S2 ). This yield is in keeping with prior clinical studies for PRP preparation, 32 although further studies are required to determine the optimal PRP therapy protocols for OD.…”

“…Submucosal injections of PRP into the olfactory cleft were well tolerated without significant adverse effects and did not worsen smell function, as previously noted in our pilot study and other studies utilizing intranasal PRP. 20 , 21 , 22 , 28 , 29 These data suggest that PRP has the potential as a safe treatment option for patients with COVID‐19 smell loss.…”

“…In their study, Steffens et al reported olfaction outcomes using a cohort of patients who underwent a single intranasal injection of PRP with a 1‐month follow‐up 22 and found that PRP treatment resulted in higher TDI scores compared with control. Our two studies differ in that ours was a randomized, blinded study that involved a placebo injection, had a longer follow‐up period of 3 months, and included only patients who had failed olfactory training.…”

“… 19 This study builds from prior pilot studies published by our group and others that demonstrated the safety of PRP in its use for OD. 20 , 21 , 22 In a murine model of anosmia, topical intranasal PRP resulted in improved olfactory function and restoration of an intact olfactory epithelium. 23 Prior single‐arm clinical trials utilizing PRP for OD demonstrated no adverse outcomes and a potential improvement in olfactory function.…”

COVID-19 related persistent olfactory disorders represent an unprecedented challenge

“…This means that although there is room for improvement, after 3 months, the risk of having long-term OD is very high. Patients should therefore be initiated to specific therapies early and, after 3 months [10] , [11] , [12] , experimental therapies may be considered, such as the injection of platelet-rich plasma into the olfactory cleft [13] .…”