Validation of a new bowel preparation scale for measuring colon cleansing for colonoscopy: the chicago bowel preparation scale

Abstract

Objectives: Current bowel preparation scales (BPSs) have significant limitations including an inability to distinguish among bowel preparations that adequately cleanse a high percentage of colons. We assessed the reliability and validity of the new Chicago BPS and compared it with existing BPSs.

Methods: We performed a prospective evaluation of the cleanliness of 150 colons. Inter-rater agreement was assessed using kappa and Pearson correlation coefficients. Each colon was rated by a gastroenterologist and physician's assistant using the Ottawa BPS, the Boston BPS, a dichotomous (adequate/inadequate) BPS (where adequate was defined as being able to visualize at least 95% of the mucosa), and the Chicago BPS.

Results: Pearson correlation coefficients between the gastroenterologists and physician's assistant for total BPS scores were 0.79 (95% confidence interval (CI): 0.73, 0.85), 0.79 (95% CI: 0.72, 0.84), and 0.84 (95% CI: 0.79, 0.88) for the Ottawa, Boston, and Chicago BPSs, respectively. Kappa coefficients for right, middle, and distal colon segment ratings were 0.66, 0.53, and 0.49, respectively, for the Ottawa BPS; 0.64, 0.66, and 0.54, respectively, for the Boston BPS; and 0.70, 0.62, and 0.63, respectively, for the Chicago BPS. Differences between the Chicago BPS and the other BPSs were not statistically significant. The Chicago BPS exhibited the best correspondence between BPS total score and the adequate/inadequate BPS.

Conclusions: This study demonstrated the validity and reliability of the Chicago BPS. The better defined grading criteria, better designed numerical ratings scale, and better correspondence between Chicago BPS total score and the adequate/inadequate BPS make the Chicago BPS an attractive alternative to the Ottawa BPS and the Boston BPS.

Figure 1

Scatter plots of gastroenterologist vs. physician's assistant (PA) total scores (n=150) for the Ottawa bowel preparation scale (BPS; top), Boston BPS (middle), and Chicago BPS (bottom). All scores are recorded as integers. Points have been “jittered”' to better display multiple observations. For example, for the Boston BPS, 84 patients had scores of 9 recorded by both raters. For the Chicago BPS, 24 patients had scores of 35 recorded by both raters and 45 patients had scores of 36 by both raters.