Platelet-rich plasma injection in the olfactory clefts of COVID-19 patients with long-term olfactory dysfunction

Objective To investigate safety, feasibility, and effectiveness of platelet-rich plasma (PRP) injection into the olfactory clefts of COVID-19 patients with persistent olfactory dysfunction (OD). Methods From March 2022 to July 2022, COVID-19 patients with persistent OD were consecutively recruited to benefit from PRP injection into the olfactory clefts. Patient pain, annoyance, time of procedure, and adverse events were evaluated. Olfactory function was evaluated at baseline and 2-month post-injection with the olfactory disorder questionnaire (ODQ) and threshold, discrimination, and identification (TDI) test. Results Eighty-seven patients with anosmia ( N = 30), hyposmia ( N = 40), or parosmia ( N = 17) with a mean OD duration of 15.7 months completed the evaluations. The PRP injection was successfully performed in all patients with a mean procedure time of 18.4 ± 3.4 min. The adverse events included transient epistaxis ( N = 31), parosmia related to xylocaine spray ( N = 10), and vasovagal episode ( N = 2). The injection procedure was evaluated as somewhat or moderately painful by 41 (47%) and 22 (25%) patients, respectively. Thirty-seven patients were assessed after 2 months post-injection. The mean ODQ and TDI scores significantly improved from baseline to 2-month post-injection ( p < 0.01). The olfactory improvement occurred after a mean of 3.6 ± 1.9 weeks. Conclusion The injection of PRP into the olfactory clefts is safe and associated with adequate patient-reported outcomes. The findings of this preliminary study suggest possible efficacy on subjective and psychophysical evaluations, but future randomized controlled studies are needed to determine the superiority of PRP injection over placebo.