Table 1.
Main studies included demographic data and treatment outcomes.
| Reference | Location | Study Design | Group Size | Mean Age | Gender Ratio (M/F | OD Identified | OD Duration | Olfactory Outcomes | Adverse Effects |
||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PRP | No PRP | PRP | No PRP | PRP | No PRP | PRP | No PRP | ||||||
| Steffens et al., 2022 [56] | Belgium | Prospective | 30 | 26 | 39 ± 12 | 44 ± 11 | 14/16 | 6/20 | Post-COVID-19 chronic olfactory dysfunction: 56 patients | 10.8 months | 9.7 months | The PRP group’s mean self-assessment of improvement in smell function was 1.8 (mild-to-moderate), significantly higher than the control group’s score of 0.3 (p < 0.001). | NA |
| El Naga et al., 2022 [57] | Egypt | Pilot study | 30 | 30 | 28.9 | 30.07 | 11/19 | 9/21 | Post-COVID-19 parosmia: 60 patients | >3.0 months | - | The VAS for parosmia showed a substantial improvement in the control group (p = 0.00148) and a highly significant improvement in the case group (p < 0.00001). Regarding the extent of improvement, there was a significant difference between the two groups that favored the case group (p = 0.002). | NA |
| Yan et al., 2022 [55] | United States | RCT | 18 | 12 | 44.6 | 43.4 | 9/9 | 6/6 | Post-COVID-19 olfactory dysfunction: 30 patients | 8.6 months | 8.9 months | Both the PRP and placebo groups demonstrated a substantial improvement in VAS scores at one and three months compared to baseline when evaluating subjective changes in smell function. Nevertheless, there was no discernible difference between the PRP and placebo groups in terms of the subjective olfaction scores using VAS at one or three months. | NA |
| Lechien et al., 2022 [54] | Belgium | Prospective | 87 | - | 41.6 ± 14.6 | - | 25/62 | - | Post-COVID-19 anosmia: 30 patients; post-COVID-19 hyposmia: 40 patients; post-COVID-19 parosmia: 17 patients | 15.7 months | - | Twenty patients (54%) and nine patients (24%) reported significant improvement in anosmia/hyposmia or parosmia, respectively, while eight patients (22%) did not report any subjective improvement in olfactory impairment. Based on the patients’ experiences, olfaction significantly improved after a mean of 3.6 ± 1.9 weeks. |
Transient epistaxis, temporary cases of parosmia due to the xylocaine spray, a small percentage had vasovagal episodes, and pain ranged from mild to moderate. |
| Lechien et al., 2023 [58] | Belgium; Italy; France | Multicenter controlled study | 81 | 78 | 43.5 ± 13.4 | 47.0 ± 11.1 | 20/61 | 26/52 | Post-COVID-19 anosmia: 55 patients; post-COVID-19 hyposmia: 79 patients; post-COVID-19 parosmia: 25 patients | 15.7 months | 11.0 months | An average improvement in subjective smell lasting 3.4 ± 1.9 weeks was noted by 85% of PRP patients. After ten weeks, the PRP group’s parosmia, life quality, TDI, and overall and sub-ODQ scores were significantly decreased. The control group experienced a significant rise in discrimination, identification, and overall TDI scores, but the ODQ score did not change. The PRP group outperformed the controls regarding 10-week TDI and ODQ scores. | NA |
| Evman et al., 2023 [59] | Turkey | RCT | 12 | 13 | 31.8 ± 6.9 | 33.5 ± 11.1 | 6/6 | 6/7 | Post-COVID-19 olfactory dysfunction: 25 patients | >12.0 months | - | The mean score for the smell identification test increased significantly in the PRP group, going from 11.42 (SD 1.17) to 15.17 (SD 0.39), and the mean score for the smell detection threshold increased correspondingly, going from 5.63 (SD 0.68) to 6.46 (SD 0.45). Conversely, the control group experienced a slight rise in the mean smell detection threshold score, going from 5.69 (SD 0.66) to 5.77 (SD 0.70), and a lesser increase in the mean smell identification test score, from 11.20 (SD 1.12) to 11.85 (SD 1.57). The statistical significance of the differences between the PRP and control groups was established (p = 0.037 and p < 0.001, respectively). | NA |
Abbreviations: PRP, Platelet-Rich Plasma; RCT, Randomized Controlled Trial; M, Male; F, Female; COVID-19, Coronavirus Disease 2019.