Topical Versus Injection PRP for Olfactory Dysfunction

Persistent olfactory dysfunction (OD) is a common sequela of viral upper respiratory tract infections, including COVID-19, and can significantly affect patients' quality of life, nutrition, and safety. Current treatment options are limited, with olfactory training being the primary evidence-based non-pharmacological therapy. Autologous platelet-rich plasma (PRP) is a concentration of platelets obtained from a patient's own blood, rich in growth factors and cytokines that promote neuronal regeneration, tissue repair, and neuroplasticity. Early clinical studies suggest PRP may improve olfactory function, but the optimal method for delivering PRP to the olfactory cleft remains unknown. This randomized controlled trial will include a total of 60 adult patients aged 18-80 years old with olfactory loss (hyposmia or anosmia) persisting for more than 3 months despite standardized olfactory training, confirmed by a reduced Sniffin' Sticks TDI score. PRP will be prepared on-site immediately before application using a standardized centrifugation protocol to achieve a platelet concentration 2-3 times above baseline. efficacy and safety of two PRP delivery methods will be compared: Intranasal Injection Group: Autologous PRP will be injected directly into the mucosa of the olfactory cleft under endoscopic guidance. After topical anesthesia with lidocaine spray and decongestion with oxymetazoline, a 25-gauge needle will be used to deliver approximately 1 mL of PRP into multiple sites along the superior nasal cavity bilaterally. Carrier-Assisted Topical Application Group: Four pieces of sterile, bioabsorbable carrier (Gelfoam sponge) will be soaked with approximately 5 mL of autologous PRP. Under endoscopic guidance, two pieces of PRP-soaked carrier will be placed gently into each side of olfactory cleft, ensuring contact with the olfactory mucosa. Carriers will remain in place for a short duration to allow diffusion of PRP before dissolving naturally or being removed. Primary Outcome: Change in TDI score from baseline to 3 months post-treatment. Secondary Outcomes: Patient-reported olfactory-related quality of life (QOD, SNOT-22, PQ), subjective improvement ratings, 20-item retronasal olfactory test, SSParoT, procedure tolerability, and adverse event rates. Post-intervention care: All participants will continue standardized daily olfactory training for at least 12 weeks after PRP administration. Follow-up visits at 2 weeks, 1 month and 3 months will assess smell function, symptom changes, and safety. This study aims to determine whether carrier-assisted topical PRP application is as effective or superior to intranasal PRP injection for improving olfactory function, while potentially offering a less invasive and more tolerable treatment approach. Results will help define optimal PRP delivery strategies for olfactory rehabilitation in clinical practice.