Department of Otolaryngology, Head and Neck Surgery, University of California San Diego School of Medicine, La Jolla, CA, USA. Department of Otolaryngology, Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, USA.
INTRODUCTION This study evaluated the use of platelet-rich plasma (PRP), an autologous blood product with supraphysiologic concentrations of growth factors, in the treatment of prolonged COVID-19 related smell loss. METHODS This multi-institutional, randomized controlled trial recruited COVID-19 patients with objectively measured smell loss (University of Pennsylvania's Smell Identification Test, UPSIT≤33) between 6-12 months. Subjects were randomized to 3 intranasal injections
of either PRP or sterile saline into their olfactory clefts. Primary outcome measure was change in Sniffin' sticks score (TDI) from baseline. Secondary endpoint measures included responder rate (achievement of a clinically significant improvement, ≥5.5 point TDI), change in individual TDI olfaction scores, and change in subjective olfaction via a visual analogue scale. RESULTS 35 subjects were recruited and 26 completed the study. PRP treatment resulted in a 3.67 point (95% CI: 0.05-7.29, p = 0.047) greater improvement in olfaction compared to the placebo group at 3-months and a higher response rate (57.1% versus 8.3%, odds ratio 12.5, 95% exact bootstrap CI 2.2-116.7). There was a greater improvement in smell discrimination following PRP treatment compared to placebo, but no difference in smell identification or threshold. There was no difference in subjective scores between PRP and placebo. No adverse effects were reported. CONCLUSION Olfactory function following COVID-19 can improve spontaneously after 6 months and can improve to a greater extent with PRP injection. This data builds on the promise of PRP to be a safe potential treatment option for patients with COVID-19 smell loss, and larger-powered studies will help further assess efficacy. This article is protected by copyright. All rights reserved.