## 3 Results
In the multivariate analyses, given time and patient, the only covariate showing a significant effect on both endoscopic scores was PNIF (\(p\) < 0.001 for both endoscopic scores) (Tables 3 and 4). \begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & **Estimate** & **Std. Error** & **df** & **t Value** & **Pr (\textgreater{}) \(\left|\left|\left|\mathbf{t}\right|\right|\right)** \\ \hline \hline
**(Intercept)** & 6.782008 & 0.370056 & 273.111323 & 18.327 & \(p\) < 0.001 \\ \hline
**T1** & \(-1.129586\) & 0.386729 & 351.734044 & \(-2.921\) & \(p\) = 0.003 \\ \hline
**T2** & \(-1.629318\) & 0.319488 & 346.085347 & \(-5.100\) & \(p\) < 0.001 \\ \hline
**T3** & \(-1.743885\) & 0.329099 & 347.207783 & \(-5.299\) & \(p\) < 0.001 \\ \hline
**T4** & \(-2.150819\) & 0.321590 & 349.366157 & \(-6.688\) & \(p\) < 0.001 \\ \hline
**T5** & \(-2.190922\) & 0.326068 & 351.438568 & \(-6.719\) & \(p\) < 0.001 \\ \hline
**T6** & \(-2.468237\) & 0.328056 & 348.364357 & \(-7.524\) & \(p\) = 0.009 \\ \hline
**PNIF** & \(-0.005115\) & 0.001955 & 345.166486 & \(-2.616\) & \(p\) < 0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Multivariate analyses to identify the effects of the variables on M-LKS changes during the follow-up. M-LKS, modified Lund–Kennedy endoscopic score; T, timepoint of visits; PNIF, peak nasal inspiratory flow. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**M-LKS**} & \multicolumn{2}{c}{**NPS**} \\ \cline{2-5}  & _Correlation_ & \(p\) _Value_ & _Correlation_ & \(p\) _Value_ \\ \hline
**SNOT-22** & 0.002 & 0.773 & 0.003 & 0.587 \\ \hline
**VAS-NO** & 0.036 & 0.399 & 0.067 & **0.038** \\ \hline
**VAS-smell** & 0.042 & 0.249 & 0.100 & **<0.001** \\ \hline
**VAS-facial pain** & \(-0.019\) & 0.692 & \(-0.035\) & 0.331 \\ \hline
**VAS-sleep** & 0.016 & 0.719 & 0.023 & 0.500 \\ \hline
**SSIT** & \(-0.997\) & 0.06 & \(-0.833\) & **0.041** \\ \hline
**PNIF** & \(-0.005\) & **0.009** & \(-0.006\) & **<0.001** \\ \hline
**ACT** & \(-0.035\) & 0.171 & \(-0.009\) & 0.640 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Correlation between M-LKS, NPS, and the main PROMs and CROMs investigated. M-LKS, modified Lund–Kennedy endoscopic score; NPS, nasal polyp score; PROMs, patient-reported outcome measures; CROMs, clinician-reported outcome measures; SNOT-22, Sinonasal Outcome Test-22; VAS, visual analog scale; NO, nasal obstruction; PNIF, peak nasal inspiratory flow; SSIT: Sniffin’ Sticks identification test. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & **Estimate** & **Std. Error** & **df** & **t Value** & **Pr (\textgreater{}) \(\left|\left|\mathbf{t}\right|\right)** \\ \hline
**(Intercept)** & 6.316710 & 0.314369 & 223.349543 & 20.093 & \(p\) < 0.001 \\ \hline
**T1** & \(-0.804958\) & 0.249023 & 400.737638 & \(-3.232\) & \(p\) = 0.001 \\ \hline
**T2** & \(-1.556601\) & 0.225303 & 399.689226 & \(-6.909\) & \(p\) < 0.001 \\ \hline
**T3** & \(-2.019193\) & 0.229423 & 400.105491 & \(-8.801\) & \(p\) < 0.001 \\ \hline
**T4** & \(-2.151421\) & 0.232079 & 400.476848 & \(-9.270\) & \(p\) < 0.001 \\ \hline
**T5** & \(-2.474594\) & 0.237109 & 401.021467 & \(-10.437\) & \(p\) < 0.001 \\ \hline
**T6** & \(-3.014599\) & 0.238966 & 398.860924 & \(-12.615\) & \(p\) < 0.001 \\ \hline
**PNIF** & \(-0.005714\) & 0.001532 & 455.698477 & \(-3.731\) & \(p\) < 0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Multivariate analyses to identify the effects of the variables on NPS changes during the follow-up. NPS, nasal polyp score; T, timepoint of visits; PNIF, peak nasal inspiratory flow.