4 Discussion
Blood eosinophil is a crucial biomarker which is in connection with
specific endotype and severity of CRSwNP(11, 17). Our previous study has
demonstrated that systemic eosinophilia (Blood eosinophil count
≥0.3×109/L) were associated with poor treatment
outcome of nasal polyps(5). However, the correlation of paranasal sinus
CT features and blood eosinophil count was rarely observed in the
previous study. Thus, identification of auxiliary clinical parameters
strongly linked to blood eosinophilia in CRSwNP could be helpful to
assess the prognosis and guide the management. The new finding in the
present research is that OC score was positively related to the level of
blood eosinophil, and an independently predictor for systemic
eosinophilia of nasal polyps. Overall, these results indicate that
olfactory cleft opacification in paranasal sinus CT scan could be a
feature for the phenotype of CRSwNP with blood eosinophilia.
In this study, the percentage of subjects with blood eosinophilia was
40% while 60% was subjects without blood eosinophilia based on the
cutpoint of 0.3×109/L. Nevertheless, the consensus
about the cutpoint of blood eosinophilia in CRSwNP has not reached. The
results about significant difference in clinical characteristics between
two subgroups confirm that eosinophilic inflammation in blood is linked
to the comorbidities such as allergy rhinitis and asthma and poor
disease control as well, which are in accordance with previous
studies(5). Although it is not clear that how blood eosinophilia acts on
the pathogenesis of CRSwNP, we could speculate that systemic
eosinophilia may contribute to local eosinophilic infiltration in nasal
mucosa and relate to structured histopathology in nasal polyps (18, 19).
In clinical practice, blood routine examination is the most direct
method that reflect the status of
eosinophilic
inflammation in blood. However, the count of peripheral blood eosinophil
is largely affected by oral glucocorticoid treatment (20, 21).
Therefore, finding additional parameters correlated to systemic
eosinophilia is necessary. Paranasal sinus CT scan as a widely used and
noninvasive test has been used to identify the phenotypes of CRSwNP(7),
predict the recurrence(10) and assess the sensitivity of glucocorticoid
for the patients(22). but few studies concentrate on the relationship
between paranasal sinus CT features and peripheral systemic
eosinophilia. Interestingly, our study showed that OC score, PES score,
ES score, SS score, ES/MS ratio and PES/AES ratio were higher in the
B-high subgroup, but only OC score as the independent risk factor was
associated with systemic eosinophilia. And for all we know, this is the
first research for reporting the significant correlation between OC area
opacification in paranasal sinus CT scan and CRSwNP with systemic
eosinophilia.
Previous study has verified that olfactory cleft opacification were
associated with olfactory dysfunction(23, 24), and could be a clinical
predictor for identifying eosinophilic CRS(25). Chen et al. (16)have
confirmed that OC score could be used to identify the airway
hyperresponsiveness in CRS, which is positively associated with blood
eosinophil counts. These reports indicated that OC score was related to
systemic eosinophilia in CRSwNP. Although the reason why OC scores were
higher in the patients with systemic eosinophilia is unclear, the
finding in this study suggests that the area of olfactory cleft with
opacification could be sensitive to the eosinophilic inflammation in the
blood.
However, several limitations in our present study are worth considering.
The size of sample size was small, and the data in this research were
short of validation in prospective cohort study. In addition, the
patients in the retrospective cohort were derived from a single tertiary
medical center, which may be not generalizable to patients with CRSwNP
in other medical institutions. Finally, 22-item Sinonasal Outcome Test
score as a clinical parameter was not included for the assessment of
disease severity.
To sum up, our study reveals that OC opacification in sinus CT is
independently associated with blood eosinophilia, and may be served as a
specific indicator of systemic eosinophilia in CRSwNP patients.