Platelet‐Rich Plasma for Treating COVID‐19‐Related Anosmia, Hyposmia, and Parosmia: A Controlled Longitudinal Study

Abstract Objective To investigate the effectiveness of platelet‐rich plasma (PRP) injection into the olfactory clefts of coronavirus disease 2019 (COVID‐19) patients with persistent anosmia, hyposmia, and parosmia. Study Design Controlled study. Setting Multicenter study. Methods From March 2022 to July 2024, 514 COVID‐19 patients undergoing PRP injection and olfactory training versus olfactory training (controls) for a persistent olfactory dysfunction (OD) were consecutively recruited from two medical centers. Subjects were evaluated from pre‐ to 3 months post‐injection with the olfactory disorder questionnaire (ODQ) and the threshold, discrimination, and identification (TDI) test. Olfactory outcomes were compared between controls and patients considering the type of OD (anosmia, hyposmia, and parosmia). Results The PRP group was composed of 416 patients with anosmia (N = 111; 26.7%), hyposmia (N = 160; 38.5%), and parosmia (N = 145; 34.9%). The baseline ODQ of patients with parosmia was significantly higher than those of the other groups ( P = .001). The increase in TDI subscores and total score was significantly higher in all PRP subgroups compared to controls ( P = 0.001). The ODQ significantly reduced from pre‐ to post‐PRP injection in hyposmia and parosmia groups ( P = 0.001). Patients with parosmia showed a significantly greater reduction in ODQ scores compared to the control group. The 3‐month TDI score was negatively influenced by the age of patients ( r s = −0.263; P = 0.001) and the duration of OD ( r s = −0.213; P = .001). Conclusion Patients with parosmia experienced a stronger impact of OD on quality of life (QoL), and showed greater QoL improvement following PRP injections compared to other groups.