Olfactory DysfunctionPhase 3TOP-INNCT07151703
Topical Versus Injection PRP for Olfactory Dysfunction
A Phase 3 study testing Intranasal Injection of Autologous PRP, Carrier-Assisted Topical Application of Autologous PRP and platelet-rich plasma in people with Olfactory Dysfunction and Anosmia, run by Taipei Veterans General Hospital, Taiwan at 1 site in Taiwan.
Trial summary
The goal of this clinical trial is to determine whether two different delivery methods of autologous platelet-rich plasma (PRP) can improve olfactory function in adults with persistent olfactory dysfunction lasting more than three months. The main questions it aims to answer are: 1. Read more about this study
- Who is it for?
- Ages 18 to 80 years
- Conditions the study is for
- Olfactory Dysfunction, Anosmia, Hyposmia
- What is being tested?
- Intranasal Injection of Autologous PRP, Carrier-Assisted Topical Application of Autologous PRP and platelet-rich plasma
- Type of treatment
- Injection or infusion, Medical device, Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 60 participants
- Where
- 1 siteTaiwan
- Study dates
- 11 Sep 2025to 31 Dec 2028
- Phase
- Phase 3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 80 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Aged between 18 and 80 years, regardless of sex
- Subjective complaint of olfactory dysfunction with confirmed hyposmia or anosmia based on standardized olfactory testing
- History of at least 3 months of prior olfactory training but with persistent olfactory complaints
Who cannot join
- Congenital anosmia
- Diagnosed neurological or structural brain abnormalities (e.g., brain tumor, major head trauma, stroke) with low likelihood of olfactory recovery
- Inability or unwillingness to comply with study procedures or follow-up assessments
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Dr. Yun-Ting Chao Principal Investigator (Attending Physician and Head of Dep.), PhD contact
Taiwan1 site, 1 recruiting
- Recruiting
Taipei Veterans General Hospital
Taipei, 112201
Yun-Ting Chao, MD, PhD, +886228757808, yunting001@gmail.com
About this study
Official title: Carrier-Assisted Topical Application Versus Intranasal Injection of Autologous Platelet-Rich Plasma for Olfactory Dysfunction: A Randomized Controlled Trial
The goal of this clinical trial is to determine whether two different delivery methods of autologous platelet-rich plasma (PRP) can improve olfactory function in adults with persistent olfactory dysfunction lasting more than three months. The main questions it aims to answer are:
- Does carrier-assisted topical application of PRP lead to comparable or better improvement in smell function than intranasal injection of PRP?
- Which method provides greater patient comfort and fewer adverse effects?
Read more
Researchers will compare carrier-assisted topical PRP application to intranasal PRP injection to see if one approach is more effective in restoring olfactory function.
Participants will:
- Receive a single PRP treatment delivered either by injection or via a PRP-soaked carrier placed into the olfactory cleft.
- Continue daily olfactory training for three months following the intervention.
- Undergo smell testing (Sniffin' Sticks) before and after treatment and complete quality-of-life questionnaires.
Read the detailed description
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.
- Conditions
- Olfactory Dysfunction, Anosmia, Hyposmia
- Being tested
- Intranasal Injection of Autologous PRP, Carrier-Assisted Topical Application of Autologous PRP, platelet-rich plasma, olfactory training
- Keywords
- Anosmia, Hyposmia, Platelet-Rich Plasma (PRP), Intranasal Injection, Randomized Controlled Trial
- Medical subject headings
- Anosmia
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Intranasal Injection of Autologous PRPProcedure or surgery
Under topical anesthesia and decongestion, approximately 1 mL of freshly prepared autologous platelet-rich plasma will be injected into multiple sites of the olfactory cleft mucosa bilaterally using a 25-gauge needle under endoscopic guidance. Single treatment session.
Carrier-Assisted Topical Application of Autologous PRPProcedure or surgery
Four pieces of sterile, bioabsorbable carrier (Gelfoam sponge) will be soaked with approximately 5 mL of freshly prepared autologous platelet-rich plasma. Under endoscopic guidance, two pieces will be placed gently into each olfactory cleft, ensuring contact with the olfactory mucosa. Carriers will remain briefly to allow PRP diffusion before dissolving naturally or being removed. Single treatment session.
platelet-rich plasmaCombination product
This study adopts a fully automated, closed-system PRP preparation technique to ensure the stability of the blood product. A total of 60 mL of whole blood is drawn and processed using the Phoenix Q1 centrifuge (TFDA Medical Device Manufacturing License No. 004461) for blood component separation in a closed, sterile environment. An optical sensor identifies and automatically collects the buffy coat layer (rich in platelets and monocytes), yielding approximately 6 mL of autologous platelet-rich plasma (PRP). The centrifugation and PRP collection process takes about 5 minutes. Compared with traditional methods requiring manual identification and collection, this approach enhances the precision and safety of centrifugation-based preparation.
olfactory trainingDevice
Participants will perform olfactory training for 12 weeks following the PRP intervention. Training is conducted twice daily using four odor bottles containing standardized odorants from Sigma-Aldrich (Germany): lemon (citronellal, #27470), rose (phenylethanol, #77861), clove (eugenol, #W246700), and eucalyptus (eucalyptol, #C80601). Each odor is sniffed gently for about 20 seconds, with a 20-second pause between bottles. Participants will record the perceived intensity of each odor in a training diary after every session.
| Study group | Role | What they receive |
|---|---|---|
| Intranasal PRP injection | Experimental | Participants in this arm will receive an intranasal injection of autologous platelet-rich plasma (PRP) into the olfactory cleft. The procedure will be conducted under local anesthesia using endoscopic guidance. All participants will also perform standardized daily olfactory training for three months following the intervention. Receives: Procedure: Intranasal Injection of Autologous PRP; Combination Product: platelet-rich plasma; Device: olfactory training |
| Topical PRP application arm | Experimental | Participants in this arm will receive a topical application of autologous PRP delivered via PRP-soaked absorbable material (Gelfoam) placed into the olfactory cleft. No needle will be used. The placement will be guided by nasal endoscopy under local anesthesia. Daily olfactory training will be continued for three months post-application. Receives: Procedure: Carrier-Assisted Topical Application of Autologous PRP; Combination Product: platelet-rich plasma; Device: olfactory training |
What is being measured
The primary outcome is the main question the study is designed to answer.
Sniffin' Sticks Olfactory Test
The Sniffin' Sticks test (Burghart Messtechnik GmbH, Holm, Germany) comprises three subtests for odor detection threshold (T), odor discrimination (D), and odor identification (I). This test employs odor-containing felt-tip pens, which are presented to participants to evaluate their olfactory performance.
In the detection threshold subtest, we employed an adaptive staircase procedure based on a three-alternative forced-choice format. Participants were tasked with differentiating a stick with a rose-like aroma (phenylethyl alcohol) from two blank sticks. Odor discrimination was assessed using 16 pen triplets, two of which contained identical odors and one stick contained a different odor. Participants were tasked with identifying the odd one out. In the odor identification subtest, participants were tasked with naming 16 common odors by selecting appropriate terms from a set of four descriptors per odor. The scores from each subtest were combined into a composite TDI score.
Measured: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention
Secondary outcomes (9)
Procedure-related pain evaluation
Visual analogue scale for pain (0-10) immediately after procedure.
Measured: during the procedure and up to 2 weeks post-intervention
Retronasal Olfactory Test
Retronasal olfactory testing was performed using standardized odorized powders/capsules presented in the oral cavity, with participants instructed to exhale through the nose and rate the perceived odor. It specifically evaluates olfactory function via the retronasal route.
Measured: pre-intervention and at 3 months post-intervention
Visual Analogus Scale for olfaction
Visual Analogus Scale for olfactory function from 0 to 10. (0 means inability of smelling and 10 means super good smell function)
Measured: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention
Questionnaire of Olfactory Disorders (QOD)
A questionnaire on olfaction-related quality of life status
Measured: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention
Beck Depression Inventory (BDI)
The Beck Depression Inventory (BDI) is a standardized self-report questionnaire measuring the severity of depressive symptoms. Olfactory loss, resulting from viral infections or other etiologies, has been associated with mood disturbances and reduced emotional well-being.
Measured: pre-intervention and 3 months post-intervention
Montreal Cognitive Assessment (MoCA)
The Montreal Cognitive Assessment (MoCA) is a widely used screening tool for mild cognitive impairment. Olfactory loss has been shown to diminish sensory stimulation to the brain, potentially affecting neural processing and cognitive function.
Measured: pre-intervention and post-3 month intervention
22-item Sinonasal Outcome Test (SNOT-22)
A questionaire reflecting the severity of symptoms and the impact of sinonasal diseases
Measured: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention
Parosmia Questionnaire (PQ)
A 4-item questionnaire to evaluate the presence, severity, and qualitative characteristics of odor distortions (parosmia).
Measured: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention
Sniffin' Sticks Parosmia Test
SSParoT (Sniffin' Sticks Parosmia Test) is a specialized assessment tool to evaluate qualitative olfactory function, particularly for the objective quantification of parosmia. It presents a series of well-characterized odorants and asks participants to rate each odor's pleasantness. From these ratings, the range of hedonic ratings and the hedonic orientation are calculated, providing quantitative measures of the breadth and direction of the participant's odor preference profile. This approach enables clinicians to identify patterns of altered odor perception and monitor changes following therapeutic interventions. The SSParoT (Sniffin' Sticks Parosmia Test) was additionally administered to participants with parosmia to calculate the range of hedonic ratings and the hedonic orientation.
Measured: pre-intervention and 3 months post-intervention
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted3 Sep 2025
- Study start11 Sep 2025
- Primary completion31 Dec 2027 (estimated)
- Study completion31 Dec 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (5)Papers the sponsor has linked to this study.
- Other trials for Olfactory DysfunctionStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Parallel two-arm design with participants randomly assigned to either carrier-assisted topical PRP application or intranasal PRP injection. Each participant receives only one type of intervention throughout the study.
- Masking
- Double blind
- Who is masked
- Participant, Outcomes assessor
- Enrolment
- 60 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Taipei Veterans General Hospital, Taiwan
- Sponsor type
- Other government
- Responsible party
- Principal investigator, Yun-Ting Chao, Taipei Veterans General Hospital, Taiwan
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07151703
- Sponsor's protocol ID
- 2025-06-010C
- Other IDs
- V115C-076
- Acronym
- TOP-IN
- Status last verified
- Sep 2026
- First submitted
- 16 Aug 2025
- Last updated
- 5 Oct 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided: The decision regarding IPD sharing will be made upon completion of the study, pending institutional policies and ethical review board recommendations.
Publications
Bae AY, Kim DH, Hwang SH. Efficacy of Platelet-Rich Plasma in the Treatment of Persistent Olfactory Impairment After COVID-19: A Systematic Review and Meta-Analysis. J Rhinol. 2024 Mar;31(1):1-7. doi: 10.18787/jr.2024.00006. Epub 2024 Mar 31.
PubMed 39664044Duffy A, Naimi B, Garvey E, Hunter S, Kumar A, Kahn C, Farquhar D, D'Souza G, Rawson N, Dalton P, Toskala E, Rabinowitz M, Rosen M, Nyquist G, Rosen D. Topical platelet-rich plasma as a possible treatment for olfactory dysfunction-A randomized controlled trial. Int Forum Allergy Rhinol. 2024 Sep;14(9):1455-1464. doi: 10.1002/alr.23363. Epub 2024 May 9.
PubMed 38722276Jiang RS, Chiang YF. The Effect of Platelet-Rich Plasma and Hyaluronic Acid Nasal Injections in the Treatment of Traumatic Olfactory Dysfunction. Ear Nose Throat J. 2024 Oct 15:1455613241291710. doi: 10.1177/01455613241291710. Online ahead of print.
PubMed 39404838Lechien JR, Le Bon SD, Saussez S. Platelet-rich plasma injection in the olfactory clefts of COVID-19 patients with long-term olfactory dysfunction. Eur Arch Otorhinolaryngol. 2023 May;280(5):2351-2358. doi: 10.1007/s00405-022-07788-8. Epub 2022 Dec 15.
PubMed 36520209Yan CH, Mundy DC, Patel ZM. The use of platelet-rich plasma in treatment of olfactory dysfunction: A pilot study. Laryngoscope Investig Otolaryngol. 2020 Feb 21;5(2):187-193. doi: 10.1002/lio2.357. eCollection 2020 Apr.
PubMed 32337347
Study at a glance
From the registry record, last updated by the sponsor on 5 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Carrier-Assisted Topical Application Versus Intranasal Injection of Autologous Platelet-Rich Plasma for Olfactory Dysfunction: A Randomized Controlled Trial
- ClinicalTrials.gov ID
- NCT07151703
- Acronym / sponsor ID
- TOP-IN / 2025-06-010C
- Conditions
- Olfactory Dysfunction, Anosmia, Hyposmia
- Keywords
- Anosmia, Hyposmia, Platelet-Rich Plasma (PRP), Intranasal Injection, Randomized Controlled Trial
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 60 participants (estimated)
- Lead sponsor
- Taipei Veterans General Hospital, TaiwanOther government
- Study start
- 11 Sep 2025 (actual)
- Primary completion
- 31 Dec 2027 (estimated)
- Study completion
- 31 Dec 2028 (estimated)
- First posted
- 3 Sep 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The goal of this clinical trial is to determine whether two different delivery methods of autologous platelet-rich plasma (PRP) can improve olfactory function in adults with persistent olfactory dysfunction lasting more than three months. The main questions it aims to answer are:
- Does carrier-assisted topical application of PRP lead to comparable or better improvement in smell function than intranasal injection of PRP?
- Which method provides greater patient comfort and fewer adverse effects?
Researchers will compare carrier-assisted topical PRP application to intranasal PRP injection to see if one approach is more effective in restoring olfactory function.
Participants will:
- Receive a single PRP treatment delivered either by injection or via a PRP-soaked carrier placed into the olfactory cleft.
- Continue daily olfactory training for three months following the intervention.
- Undergo smell testing (Sniffin' Sticks) before and after treatment and complete quality-of-life questionnaires.
Detailed description
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.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind (participant, outcomes assessor)
- Number of arms
- 2
- Model description
- Parallel two-arm design with participants randomly assigned to either carrier-assisted topical PRP application or intranasal PRP injection. Each participant receives only one type of intervention throughout the study.
| Arm | Type | Receives |
|---|---|---|
| Intranasal PRP injection | Experimental | Procedure: Intranasal Injection of Autologous PRP, Combination Product: platelet-rich plasma, Device: olfactory trainingParticipants in this arm will receive an intranasal injection of autologous platelet-rich plasma (PRP) into the olfactory cleft. The procedure will be conducted under local anesthesia using endoscopic guidance. All participants will also perform standardized daily olfactory training for three months following the intervention. |
| Topical PRP application arm | Experimental | Procedure: Carrier-Assisted Topical Application of Autologous PRP, Combination Product: platelet-rich plasma, Device: olfactory trainingParticipants in this arm will receive a topical application of autologous PRP delivered via PRP-soaked absorbable material (Gelfoam) placed into the olfactory cleft. No needle will be used. The placement will be guided by nasal endoscopy under local anesthesia. Daily olfactory training will be continued for three months post-application. |
Who may qualify
- Ages
- 18 to 80 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- Aged between 18 and 80 years, regardless of sex
- Subjective complaint of olfactory dysfunction with confirmed hyposmia or anosmia based on standardized olfactory testing
- History of at least 3 months of prior olfactory training but with persistent olfactory complaints
Key exclusion criteria (3 listed)
- Congenital anosmia
- Diagnosed neurological or structural brain abnormalities (e.g., brain tumor, major head trauma, stroke) with low likelihood of olfactory recovery
- Inability or unwillingness to comply with study procedures or follow-up assessments
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Intranasal Injection of Autologous PRPUnder topical anesthesia and decongestion, approximately 1 mL of freshly prepared autologous platelet-rich plasma will be injected into multiple sites of the olfactory cleft mucosa bilaterally using a 25-gauge needle under endoscopic guidance. Single treatment session. | Procedure or surgery | Intranasal PRP injection |
| Carrier-Assisted Topical Application of Autologous PRPFour pieces of sterile, bioabsorbable carrier (Gelfoam sponge) will be soaked with approximately 5 mL of freshly prepared autologous platelet-rich plasma. Under endoscopic guidance, two pieces will be placed gently into each olfactory cleft, ensuring contact with the olfactory mucosa. Carriers will remain briefly to allow PRP diffusion before dissolving naturally or being removed. Single treatment session. | Procedure or surgery | Topical PRP application arm |
| platelet-rich plasmaThis study adopts a fully automated, closed-system PRP preparation technique to ensure the stability of the blood product. A total of 60 mL of whole blood is drawn and processed using the Phoenix Q1 centrifuge (TFDA Medical Device Manufacturing License No. 004461) for blood component separation in a closed, sterile environment. An optical sensor identifies and automatically collects the buffy coat layer (rich in platelets and monocytes), yielding approximately 6 mL of autologous platelet-rich plasma (PRP). The centrifugation and PRP collection process takes about 5 minutes. Compared with traditional methods requiring manual identification and collection, this approach enhances the precision and safety of centrifugation-based preparation. | Combination product | Intranasal PRP injection, Topical PRP application arm |
| olfactory trainingParticipants will perform olfactory training for 12 weeks following the PRP intervention. Training is conducted twice daily using four odor bottles containing standardized odorants from Sigma-Aldrich (Germany): lemon (citronellal, #27470), rose (phenylethanol, #77861), clove (eugenol, #W246700), and eucalyptus (eucalyptol, #C80601). Each odor is sniffed gently for about 20 seconds, with a 20-second pause between bottles. Participants will record the perceived intensity of each odor in a training diary after every session. | Device | Intranasal PRP injection, Topical PRP application arm |
Primary outcome
Sniffin' Sticks Olfactory Test
Time frame: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention
The Sniffin' Sticks test (Burghart Messtechnik GmbH, Holm, Germany) comprises three subtests for odor detection threshold (T), odor discrimination (D), and odor identification (I). This test employs odor-containing felt-tip pens, which are presented to participants to evaluate their olfactory performance. In the detection threshold subtest, we employed an adaptive staircase procedure based on a three-alternative forced-choice format. Participants were tasked with differentiating a stick with a rose-like aroma (phenylethyl alcohol) from two blank sticks. Odor discrimination was assessed using 16 pen triplets, two of which contained identical odors and one stick contained a different odor. Participants were tasked with identifying the odd one out. In the odor identification subtest, participants were tasked with naming 16 common odors by selecting appropriate terms from a set of four descriptors per odor. The scores from each subtest were combined into a composite TDI score.
9 secondary outcomes
Procedure-related pain evaluation
Time frame: during the procedure and up to 2 weeks post-intervention
Retronasal Olfactory Test
Time frame: pre-intervention and at 3 months post-intervention
Visual Analogus Scale for olfaction
Time frame: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention
Questionnaire of Olfactory Disorders (QOD)
Time frame: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention
Beck Depression Inventory (BDI)
Time frame: pre-intervention and 3 months post-intervention
Montreal Cognitive Assessment (MoCA)
Time frame: pre-intervention and post-3 month intervention
22-item Sinonasal Outcome Test (SNOT-22)
Time frame: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention
Parosmia Questionnaire (PQ)
Time frame: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention
Sniffin' Sticks Parosmia Test
Time frame: pre-intervention and 3 months post-intervention
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 5 Oct 2026.
- Background: PubMed 39664044Bae AY, Kim DH, Hwang SH. Efficacy of Platelet-Rich Plasma in the Treatment of Persistent Olfactory Impairment After COVID-19: A Systematic Review and Meta-Analysis. J Rhinol. 2024 Mar;31(1):1-7. doi: 10.18787/jr.2024.00006. Epub 2024 Mar 31.
- Background: PubMed 38722276Duffy A, Naimi B, Garvey E, Hunter S, Kumar A, Kahn C, Farquhar D, D'Souza G, Rawson N, Dalton P, Toskala E, Rabinowitz M, Rosen M, Nyquist G, Rosen D. Topical platelet-rich plasma as a possible treatment for olfactory dysfunction-A randomized controlled trial. Int Forum Allergy Rhinol. 2024 Sep;14(9):1455-1464. doi: 10.1002/alr.23363. Epub 2024 May 9.
- Background: PubMed 39404838Jiang RS, Chiang YF. The Effect of Platelet-Rich Plasma and Hyaluronic Acid Nasal Injections in the Treatment of Traumatic Olfactory Dysfunction. Ear Nose Throat J. 2024 Oct 15:1455613241291710. doi: 10.1177/01455613241291710. Online ahead of print.
- Background: PubMed 36520209Lechien JR, Le Bon SD, Saussez S. Platelet-rich plasma injection in the olfactory clefts of COVID-19 patients with long-term olfactory dysfunction. Eur Arch Otorhinolaryngol. 2023 May;280(5):2351-2358. doi: 10.1007/s00405-022-07788-8. Epub 2022 Dec 15.
- Background: PubMed 32337347Yan CH, Mundy DC, Patel ZM. The use of platelet-rich plasma in treatment of olfactory dysfunction: A pilot study. Laryngoscope Investig Otolaryngol. 2020 Feb 21;5(2):187-193. doi: 10.1002/lio2.357. eCollection 2020 Apr.
- Individual participant dataSharing planned: Undecided. The decision regarding IPD sharing will be made upon completion of the study, pending institutional policies and ethical review board recommendations.
Related trials for Olfactory Dysfunction
Not yet recruitingEarly Phase 1
In Vivo Imaging of the Olfactory Epithelium Using Confocal Laser Endomicroscopy
Endonasal Surgery, Endoscopic Sinus Surgery
RecruitingPhase 2
Impact of Smell Testing on Health Outcomes
Olfactory Dysfunction, Wellbeing
Not yet recruiting
Acupuncture for Post-traumatic Olfactory Dysfunction: A Randomized Controlled Trial
Post-traumatic Olfactory Dysfunction, Traumatic Brain Injury
Not yet recruiting
Position-Directed Budesonide Nasal Drops for CRS-associated Olfactory Dysfunction
Chronic Rhinosinusitis (CRS), Olfactory Dysfunction
Not yet recruitingObservational study
Neural Dissimilarity in Patients With Chronic Rhinosinusitis With Nasal Polyps Treated With Biologics
Olfactory Dysfunction, Chronic Rhinosinusitis With Nasal Polyps (CRSwNP)
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Dr. Yun-Ting Chao Principal Investigator (Attending Physician and Head of Dep.), PhD contact
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing Intranasal Injection of Autologous PRP, Carrier-Assisted Topical Application of Autologous PRP and platelet-rich plasma in people with Olfactory Dysfunction and Anosmia, run by Taipei Veterans General Hospital, Taiwan at 1 site in Taiwan.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 5 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Taiwan. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Dr. Yun-Ting Chao Principal Investigator (Attending Physician and Head of Dep.), PhD (886-2-2875-7337 ext. 122, yunting001@gmail.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Sniffin' Sticks Olfactory Test (time frame: pre-intervention and at 1 and 3 months (may extend to 6 and 12 months) post-intervention). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07151703, which also lists 5 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 5 Oct 2026.