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did not associate with treatment response inflammatory burden 9,14 . However, studies are
rates. In fact, the lack of correlation between limited by small sample sizes, heterogeneous
injection timing and degree of improvement patient populations, and PRP preparation
had similarly been reported in the randomized and administration variations. Therefore,
trial . Moreover, it is known that spontaneous more extensive and well-designed studies
10
recovery in post-viral olfactory dysfunction can are needed to confirm these findings and
potentially occur for longer than one year . establish optimal treatment protocols.
18
Therefore, we believe that PRP treatment This study has its limitations. A drawback is
should also be offered to patients with longer the absence of randomization and placebo
lasting dysfunction. In addition, our results arm in research with few patients. We
showed only mild or no procedural discomfort acknowledge that a control group would be
(VAS score ≤ 2) in all patients. Nevertheless, ideal for determining PRP effectiveness and
in our experience, despite being reasonably ruling out the placebo effect. It should also
painless, the fear of anticipation makes it be noted that our PRP process included a low
impactful in some patients. Hence, instead dose of sodium citrate as an anticoagulant
of using an empirical cycle of three separate for PRP purification. Sodium citrate has
injections within 2-week intervals , we prefer been proven to have good platelet recovery
10
to perform only one injection with ulterior re- and mesenchymal stromal cell proliferation
assessment. compared to other anticoagulants, making
This work also unveiled a peculiar mismatch it an ideal anticoagulant. However, some
between the VAS and OPT scores at 1 and research suggests that sodium citrate can
3 months, since the correlation between itself ameliorate olfactory impairment in
objective and subjective measurements was postinfectious olfactory loss . In this way,
25
only significant at baseline. This had been there might be a synergic effect of PRP when
previously observed in our pCIOD medical combined with sodium citrate yielding a 3- to
treatment protocol and was somewhat 5-fold increase in growth factor production .
1
9
described in the PRP pilot study . Analyzing Thus, this fact could have influenced the
9
Figure 4, one can note that a more substantial results. Also, for convenience, only OPT was
VAS score improvement was reached at the 3 measured in the psychophysical domain, so
months assessment. This may reflect the delay that identification and discrimination were
between the peripheral neuronal regeneration not evaluated in this sample. Also, in order
and central cortical integration. Alternatively, it to homogenize the sample, only pCIOD
may imply that an individual's everyday smell patients were included, although the initial
dysfunction experience has subtleties that our pilot study of PRP injection included other
olfactory test battery cannot fully capture. etiologies of olfactory dysfunction . Our study
9
PRP is being used more frequently in many has its own strengths as well. It is the first to
other surgical specialties . Concerning describe an effective single-site PRP injection
19
Otorhinolaryngology, PRP application is protocol applied to olfactory dysfunction.
not limited to the olfactory science, as it has Also, it describes therapeutic efficacy of PRP
previously been suggested as beneficial in injection in patients suffering from pCIOD for
nasal surgery 20–22 , otology and cleft palate ≥ 12 months.
23
surgery . The exact mechanisms of how
24
PRP may improve olfactory function are Conclusion
not fully understood. Some suggest that We comprehensively described a new single-
the high concentration of platelet derived site PRP injection protocol for olfactory
molecules may stimulate the regeneration dysfunction management. The olfactory
of olfactory neurons, improve the function outcomes of such intervention on pCIOD
of the olfactory epithelium and halt the patients were explored. In line with very
352 Revista Portuguesa de Otorrinolaringologia - Cirurgia de Cabeça e Pescoço
