Navigating the efficacy, safety and outcome of intranasal platelet-rich plasma for persistent olfactory loss: a systematic review and meta-analysis

BACKGROUND: Persistent olfactory dysfunction (OD) poses a significant clinical challenge with limited therapeutic options. Intranasal platelet-rich plasma (PRP), an autologous source of regenerative growth factors, presents a biologically plausible intervention, yet its efficacy across various OD etiologies remains synthetically underexplored. METHODS: This systematic review and meta-analysis adhered to PRISMA guidelines. A comprehensive search of PubMed/MEDLINE, Web of Science, and Cochrane Library (2010-2025) identified studies assessing intranasal PRP for persistent OD (> 6 months). Random-effects models pooled standardized mean differences (SMD) for objective (e.g., Sniffin' Sticks TDI) and subjective outcomes. RESULTS: Seven studies (n = 473) were included. Meta-analysis of controlled studies (n = 314) demonstrated a moderate, significant improvement in objective olfactory scores favoring PRP over control (SMD 0.61, 95% CI 0.38-0.84). The pooled mean TDI change from baseline was 7.73 points (95% CI 6.59-8.87), exceeding the minimal clinically important difference of 5.5 points. Benefits were observed across post-COVID-19, post-viral, and post-traumatic etiologies. Adverse events were predominantly mild and transient (e.g., epistaxis). CONCLUSION: Intranasal PRP appears to be a generally well-tolerated and promising therapeutic strategy, yielding clinically meaningful improvements in persistent OD of diverse origins. However, the evidence remains preliminary and should be interpreted cautiously, as it is based on only two small RCTs plus non-randomized or single-arm studies. Future studies must optimize its protocol and evaluate its potential synergy with standard therapies like olfactory training.