Reliability and validity of a modified Bristol Stool Form Scale for children

Objectives: This study sought to: evaluate the ability of children to reliably use a modified Bristol Stool Form Scale for Children (mBSFS-C), evaluate criterion-related validity of the mBSFS-C, and identify the lower age limit for mBSFS-C use.

Study design: The mBSFS-C comprises 5 stool form types described and depicted in drawings. Children 3 to 18 years old rated stool form for 10 stool photographs. Because of low reliability when stool form descriptors were not read aloud (n = 119), a subsequent sample of children (n = 191) rated photographs with descriptors read.

Results: Intraclass correlation coefficients for descriptor-unread versus -read samples were 0.62 and 0.79, respectively. Children were increasingly reliable with age. Percentage of correct ratings varied with stool form type, but generally increased with age. With descriptors unread, children 8 years and older demonstrated acceptable interobserver reliability, with >78% of ratings correct. With descriptors read, children 6 years and older demonstrated acceptable reliability, with >80% of ratings correct.

Conclusions: The mBSFS-C is reliable and valid for use by children, with age 6 years being the lower limit for scale use with descriptors read and age 8 years being the lower limit without descriptors read. We anticipate that the mBSFS-C can be effectively used in pediatric clinical and research settings.