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

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 (≥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.

Abbreviations: ASGE, American Society for Gastrointestinal Endoscopy, BBPS, Boston bowel preparation scale, DVD, digital video disc, ICC, intraclass correlation coefficient