Objective: Rectal cancer is often treated with surgery such as ostomy or anastomosis. The Bowel Function Instrument (BFI) is a valid and reliable 18-item measure of physical bowel symptoms. Some items on the BFI do not apply to those with ostomies. We reanalyzed data from a previous validation study to inform the best method for scoring the BFI for both people with ostomies and anastomosis.
Methods: People (n = 575) with rectal cancer treated with ostomy (n = 181, 31 %) or anastomosis (n = 394, 69 %) completed the BFI and Short Form 12 (SF12) measure on a mailed survey. The full BFI has three subscales and a total score based on 14 items: soilage/urgency (4 items); frequency of bowel movements (6 items); and dietary changes (4 items). We used confirmatory factor analysis (CFA) to examine two versions (8-item, 11-item) of the BFI adapted for use with both ostomy and anastomosis. We also examined reliability and validity of the version supported by the CFA.
Results: CFA results supported the 8-item BFI that included only the soilage/urgency items and dietary changes items but not the frequency items. The 8-item BFI was reliable (Cronbach's alpha of 0.788). The 8-item BFI score significantly correlated with all SF12 subscales with Pearson correlations ranging from 0.115 (Vitality) to 0.318 (social function).
Conclusions: The 8-item version of the BFI was valid and reliable as a total score for people with ostomy or anastomosis. The 8-item BFI may be useful for monitoring bowel function during and after treatment for rectal cancer.
Keywords: Neoplasm; Patient-reported outcomes; Psychometrics; Rectal cancer.
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