## 4 Discussion  
This study compares two widely adopted endoscopic scoring systems for assessing patients with CRSwNP [9; 20], specifically evaluating their changes following the administration of dupilumab as an add-on therapy for severe CRSwNP. The results demonstrated a significant and sustained decrease in both NPS and M-LKS over the study period, without differences between the two, confirming what was previously observed in a study conducted with [21], and highlighting their value as key objective measures for monitoring disease improvement during treatment. This response underscores the powerful anti-type 2 inflammatory effects of dupilumab on nasal mucosal swelling, nasal secretions, and polyp burden, which are pivotal to the pathophysiology of CRSwNP. Remarkably, the absence of a statistically significant divergence between the two endoscopic scores suggests that these scales are equally effective in capturing the endoscopic response to treatment, further validating their reliability for assessing disease progression and treatment response in this patient population. A similar pattern of improvement was also observed in all the other considered measurements, included in both PROMs and CROMs. This reflects dupilumab's outstanding efficacy across multiple domains of disease burden, underscoring its ability to significantly alleviate both symptoms and disease severity throughout the study period. Notably, when looking at correlations, no statistically significant correlation was found between SNOT-22 and both endoscopic scores. Despite being one of the few validated PROMs for CRS, the discrepancy between SNOT-22 and the evaluated endoscopic scores is consistent to what has already emerged from previous studies in the literature [22]. This divergence contributes to demonstrate once again the absence of statistically significant correlation between the majority of PROMs and CROMs in functional sinonasal diseases. This aspect might be justified by the fact that PROMs, evaluating symptoms burden, are prone to be strongly influenced by patient subjectivity. On the other hand, significant correlations were observed between the endoscopic scores and the CROMs used to assess nasal patency and olfactory function. Specifically, PNIF demonstrated a significant negative correlation with both M-LKS and NPS. Similarly, SSIT negatively correlated with NPS and M-LKS. These findings suggest that the NP shrinkage, assessed by both endoscopic scores, surely has a significant positive effect on both patients' nasal patency and olfactory function. However, the evaluation of NP volume clearly appears to have a distinct influence on the two endoscopic scores, specifically being the only factor considered by NPS, while representing just one of different features evaluated by M-LKS. Notably, there were no significant differences in the respective NPS and M-LKS correlations with PNIF and SSIT. This can be explained by the fact that in the M-LKS, either the NP size reduction is impactful enough to significantly reduce the global system score, or the simultaneous mucosal edema and secretions reduction may synergically contribute to improve both PNIF and SSIT, leading to a decrease in the overall score comparable to the NPS reduction. On the other hand, considering that NP consists of only one of the predominant manifestations of nasal inflammation, the sole assessment of their reduction over time might be sufficient to monitor the decrease in the inflammatory burden in the majority of CRSwNP patients undergoing treatment with dupilumab. This is especially valuable in non-research setting patient evaluation, where the use of different and potentially redundant scores might unnecessarily and excessively prolong the duration of patients' assessment. Focusing on the correlation between both endoscopic score and the olfactory impairment, the olfactory recovery can likely be the result of an increased ventilation of the olfactory cleft followed by NP shrinkage, allowing a higher concentration of odorants to reach the olfactory epithelium [23].