Development and validation of the disease-specific Short Bowel Syndrome-Quality of Life (SBS-QoL™) scale

Abstract

Background & aims: Subjects with short bowel syndrome (SBS) have impaired quality of life (QoL). No disease-specific instrument has been available to measure treatment-induced changes in QoL over time. Therefore, the aim was to develop and validate an SBS-specific QoL scale.

Methods: Classical test theory and Food and Drug Administration (FDA) guidance were applied for development and validation of the SBS-QoL™. Procedures included item generation and raw scale construction. Factor analysis, construct validity and internal consistency were assessed in a non-interventional observation, test re-test reliability and responsiveness in a randomised clinical study.

Results: The SBS-QoL™ comprises 17 items including two subscales. Subjects assessed the scale as easy to handle and comprehensible. Good construct validity was shown by comparison with the Home Parenteral Nutrition-Quality Of Life questionnaire as an external scale, which yielded moderately high correlation (r ≥ 0.7). High internal consistency was demonstrated (Cronbach's alpha: 0.94). Also the test re-test reliability was high (r ≥ 0.95), indicating reliable reproducibility of results. The Responsiveness Index (1.84) indicated the ability of the scale to detect changes in QoL over time.

Conclusions: The SBS-QoL™ is an easy to handle and comprehensible SBS-specific subject-reported QoL scale. It is valid, reliable and sensitive with excellent psychometric characteristics to measure treatment-induced changes in QoL over time in subjects with SBS.

Trial registration: ClinicalTrials.gov NCT00798967.

Keywords: CTT; Classical test theory; Quality of life (QoL); RI; Responsiveness Index; Scale; Short bowel syndrome (SBS); VAS; Validation; Visual Analogue Scale.