Psychometric testing of the Skull Base Inventory health-related quality of life questionnaire in a multi-institutional study of patients undergoing open and endoscopic surgery.

Purpose: The skull base inventory (SBI) was developed to better assess health-related quality of life (HR-QOL) in patients with anterior and central skull base neoplasms treated by endoscopic and open approaches. The primary objective of this study was to prospectively assess the psychometric properties of the SBI.
Methods: This study is part of a multi-center study of patients undergoing endoscopic and open procedures completed between 2012 and 2018. Participants were eligible if they were over 18 years of age; had benign or malignant anterior, antero-lateral, or central skull base tumors; and required either an open or endoscopic skull base surgical approach. In order to assess the psychometric properties of the SBI, patients completed the instrument at six time points (preoperative, 2 weeks, 3 months, 6 months, 12 months postoperative). Patients also completed the Anterior Skull Base (ASB) questionnaire and the Sinonasal Outcome Test (SNOT-22) to allow comparison to the SBI.
Results: One hundred and eighty-seven patients were included across five centers, with 121 having an endoscopic procedure. Internal consistency (Cronbach's alpha = 0.95) and test-retest at 12 months and 12 months plus 2 weeks (intraclass correlation > 0.90) were excellent. Concurrent validity was demonstrated by very strong correlation between total SBI scores and ASB scores (r = 0.810 to 0.869, p < 0.001) and moderate correlation between nasal domain SBI scores and SNOT-22 scores (r = - 0.616 to - 0.738, p < 0.001). Convergent validity was demonstrated by moderate correlation between change in SBI scores and global QOL change (r _s  = 0.4942, p < 0.001). The minimally important clinical difference (global HR-QOL change of "a little better" or "a little worse") was 6.0.
Conclusion: The SBI questionnaire is reliable and valid for patients treated by both endoscopic and open approaches and can be used for assessment of HR-QOL in these settings.