Preliminary Reliability and Validity of the Skull Base Inventory (SBI) Quality-of-Life Questionnaire

Background: The Skull Base Inventory (SBI) was developed to assess quality of life for patients undergoing endoscopic or open approaches for anterior and central skull base pathology. Discriminative and evaluative properties for this instrument have not yet been established.

Methods: The 41-item SBI was administered in a cross-sectional fashion to patients who previously had skull base surgery at varying points after treatment. Internal consistency within domains, item test-retest reliability, construct validity, floor and ceiling effects, and minimally important clinic differences were determined. Four constructs were evaluated with the following a priori hypotheses: patients with (1) malignancies versus benign histology, (2) history of radiation versus none, and (3) recurrences versus none will have poorer scores; and (4) items deemed relevant by respondents will be associated with poorer scores than those deemed irrelevant.

Results: Fifty-two patients (24 M, 28 F) with mean age of 46.4 years (SD 14.7) completed the questionnaire; 32 had endoscopic approaches, and 20 had open approaches. Internal consistency was good (>0.7 and <0.95) for all domains accept one. Test-retest reliability was good (>0.70) for 38 of 41 items. Four constructs were evaluated and three were consistent with a priori hypotheses (P < 0.05). The instrument failed to confirm the hypothesis that malignant tumors are associated with poorer scores than benign. No floor effects existed; however, 6 of 11 domains demonstrated ceiling effects. The minimally important difference was determined to be 1 unit on the 7-point Likert scale.

Conclusions: The SBI demonstrates some preliminary reliability and validity properties for discriminative use. Further longitudinal studies are needed to better establish validity and evaluative properties of the instrument.