Effectiveness of Multiple Platelet-Rich Plasma Injections for Olfactory Dysfunction.

ImportanceThe injections of platelet-rich plasma (PRP) in the olfactory clefts of patients with olfactory dysfunction (OD) is an emerging treatment. To date, no study investigated the effectiveness of multiple PRP injections.ObjectiveTo evaluate the effectiveness and usefulness of multiple injections of PRP in the olfactory clefts of patients with OD.DesignProspective controlled study.SettingMonocentric medical center.ParticipantsPatients with long-lasting OD treated with PRP injections and controls who underwent olfactory training with multiple psychophysical olfactory assessments.InterventionTwo PRP injections into the olfactory clefts at 4- to 6-month intervals.Main OutcomesOutcomes included adverse events, dose-effect relationships, and olfactory function changes measured by threshold, discrimination, and identification (TDI) testing with minimal clinically important difference (MCID).ResultsEighty-three subjects completed the evaluations. Patients had anosmia (n = 39), hyposmia (n = 27), and parosmia (n = 17). The mean duration of OD was 49.1 ± 46.9 months. Seventy-seven patients received 2 injections. Transient epistaxis was the primary adverse event (46.2%). The mean injected PRP volume ranged from 1.4 to 1.7 mL. TDI significantly increased after both first and second injections across all OD subgroups. MCID was achieved in 49.4% after a first injection and 28.9% after a second. MCID was reached in 63 cases (75.9%) from baseline to final evaluation. Baseline TDI strongly predicted post-second injection TDI (rs = .919; P = .001), but the first PRP response didn't significantly predict second response (rs = -.201; P = .069). TDI did not significantly change in the control groups. MCID was achieved in 22.2% and 40% controls at the first and second TDI evaluations.Conclusion and RelevanceTwo injections of PRP demonstrate significant improvement in psychophysical olfactory evaluations. Future studies are needed to determine the optimal number of injections and identify predictors of therapeutic effectiveness.