Statistical Analysis
Pilot study: Comprehensibility was calculated as the percentage of patients who stated that the instrument was understandable. Feasibility was assessed by examining the number of missing responses on the returned questionnaires. Internal consistency analysis was performed with the Cronbach α coefficient.
A content validity index (CVI) based on expert ratings of relevance was used to quantify content validity. We calculated the CVI for each item (I-CVI) and for the overall scale (OS-CVI). The I-CVI was calculated as the number of experts giving a rating of either 3 or 4, divided by the number of experts. To determine OS-CVI, we calculated the I-CVI of each item on the questionnaire and then computed the average I-CVI across items[18] (Supplementary Table 2).
Validation process: Feasibility was assessed by examining the number of missing responses on the returned questionnaires and the time required to complete the questionnaire in minutes.A reliability analysis was conducted, following the test-retest procedure. Internal consistency analysis was performed with the Cronbach α coefficient. Construct validity was assessed using known groups validity and convergent/divergent validity. The Mann-Whitney U test was used to test for statistically significant differences between two subgroups of frequency (fewer than 2 episodes and more than 4 episodes per week). Convergent/divergent validity was assessed by correlating CSOC scores with SF-36 and VAS using the Pearson correlation coefficient. Responsiveness was evaluated comparing CSOC results before and after sialendoscopy by paired sample t-test.