The Boston bowel preparation scale: a valid and reliable instrument for colonoscopy-oriented research

Abstract

Background: Few bowel-preparation rating scales have been validated. Most scales were intended for comparing oral purgatives and fail to account for washing and/or suctioning by the endoscopist. This limits their utility in studies of colonoscopy outcomes, such as polyp-detection rates.

Objective: To develop a valid and reliable scale for use in colonoscopy outcomes research.

Setting: Academic medical center.

Methods: We developed the Boston bowel preparation scale (BBPS), a 10-point scale that assesses bowel preparation after all cleansing maneuvers are completed by the endoscopist. We assessed interobserver and intraobserver reliability by using video footage of colonoscopies viewed on 2 separate occasions by 22 clinicians. We then applied the BBPS prospectively during screening colonoscopies and compared BBPS scores with clinically meaningful outcomes, including polyp-detection rates and procedure times.

Results: The intraclass correlation coefficient (a measure of interobserver reliability) for BBPS scores was 0.74. The weighted kappa (a measure of intraobserver reliability) for scores was 0.77 (95% CI, 0.66-0.87). During 633 screening colonoscopies, the mean (SD) BBPS score was 6.0 +/- 1.6. Higher BBPS scores (> or =5 vs <5) were associated with a higher polyp-detection rate (40% vs 24%, P < .02). BBPS scores were inversely correlated with colonoscope insertion (r = -0.16, P < .003) and withdrawal (r = -0.23, P < .001) times.

Limitations: Single-center study.

Conclusions: The BBPS is a valid and reliable measure of bowel preparation. It may be well suited to colonoscopy outcomes research because it reflects the colon's cleanliness during the inspection phase of the procedure.

Figure 1

The Boston Bowel Preparation Scale (BBPS). A, segment score 0: unprepared colon segment with mucosa not seen due to solid stool that cannot be cleared. B, segment score 1: portion of mucosa of the colon segment seen, but other areas of the colon segment not well seen due to staining, residual stool and/or opaque liquid. C, segment score 2: minor amount of residual staining, small fragments of stool and/or opaque liquid, but mucosa of colon segment seen well. D, segment score 3: entire mucosa of colon segment seen well with no residual staining, small fragments of stool and/or opaque liquid

Figure 1

The Boston Bowel Preparation Scale (BBPS). A, segment score 0: unprepared colon segment with mucosa not seen due to solid stool that cannot be cleared. B, segment score 1: portion of mucosa of the colon segment seen, but other areas of the colon segment not well seen due to staining, residual stool and/or opaque liquid. C, segment score 2: minor amount of residual staining, small fragments of stool and/or opaque liquid, but mucosa of colon segment seen well. D, segment score 3: entire mucosa of colon segment seen well with no residual staining, small fragments of stool and/or opaque liquid

Figure 1

The Boston Bowel Preparation Scale (BBPS). A, segment score 0: unprepared colon segment with mucosa not seen due to solid stool that cannot be cleared. B, segment score 1: portion of mucosa of the colon segment seen, but other areas of the colon segment not well seen due to staining, residual stool and/or opaque liquid. C, segment score 2: minor amount of residual staining, small fragments of stool and/or opaque liquid, but mucosa of colon segment seen well. D, segment score 3: entire mucosa of colon segment seen well with no residual staining, small fragments of stool and/or opaque liquid

Figure 1

The Boston Bowel Preparation Scale (BBPS). A, segment score 0: unprepared colon segment with mucosa not seen due to solid stool that cannot be cleared. B, segment score 1: portion of mucosa of the colon segment seen, but other areas of the colon segment not well seen due to staining, residual stool and/or opaque liquid. C, segment score 2: minor amount of residual staining, small fragments of stool and/or opaque liquid, but mucosa of colon segment seen well. D, segment score 3: entire mucosa of colon segment seen well with no residual staining, small fragments of stool and/or opaque liquid

Figure 2

Distribution of Boston Bowel Preparation Scale scores applied during 633 screening colonoscopies. The distribution approximates a bell-shaped curve with a median score of 6 and an interquartile range of 6-7.

Figure 3

We determined the mean (SD) Boston Bowel Preparation Scale score (y-axis) assigned for each categorical bowel preparation rating (x-axis) observed during 633 screening colonoscopies. The decreasing trend in scores across decreasing categorical preparation qualities was statistically significant (p<0.001).