Use of Bristol Stool Form Scale to predict the adequacy of bowel preparation - a prospective study

Inadequate bowel preparation continues to be a substantial problem for colonoscopy. The seven-point Bristol Stool Form Scale (BSFS) has been associated with delayed colonic transit in adults. We evaluated the utility of the BSFS to identify patients more likely to present with an inadequate preparation.

Two large community-based academic medical centres in New Jersey, USA, studied a prospective cohort of 411 consecutive patients undergoing outpatient colonoscopy who were prescribed similar bowel preparations. The BSFS and several other study variables were collected by gastroenterology fellows during an outpatient visit prior to scheduling colonoscopy. All colonoscopy examinations were performed in the morning by a gastroenterologist who graded the adequacy of bowel preparation. Inadequate preparation was defined as one resulting in a repeat colonoscopy at a shorter time interval than would generally be recommended based solely on risk factors or pathological findings. The ability of study variables to discriminate those who did or did not have an adequate preparation was summarized by the c-statistic. The relationship between variables that provided some discrimination and the probability of an adequate preparation was modelled using logistic regression.

The mean age of the study sample was 56 ± 8 (SD) years and 63% were women. Bowel preparation was adequate in 337 (82%) of the patients. The BSFS ratings ranged from 1 to 7. The score was <3 in 144 (35%) indicating lower gastrointestinal motility. There was a statistically significant association between the score and the probability of an adequate bowel preparation (odds ratio 1.4; 95% confidence interval 1.2-1.7; P < 0.001) and the c-statistic was 0.64 (0.58-0.70).

Use of the BSFS may help identify patients for whom standard bowel preparation most probably will not be adequate.