Effect of quality of bowel preparation on quality indicators of adenoma detection rates and colonoscopy completion rates

Background and aim: Adequate bowel preparation is important for safe and effective colonoscopy. Quality indicators (QI) for colonoscopy include achieving at least 95% completion rate and an adenoma detection rate (ADR) of at least 25% in average-risk men and 15% in average-risk women aged over 50. Our aim was to investigate the impact of bowel preparation on ADR and colonoscopy completion rates. Methods: This retrospective cohort study included patients who underwent colonoscopy between January 2008 and December 2009. The main outcome measurements were ADR and colonoscopy completion rates to the cecum. Results: A total of 2519 patients was included; 1030 (41.0%) had excellent preparation, 1145 (45.5%) good-, 240 (9.5%) fair-, and 104 (4.1%) poor preparation. Colonoscopy completion rates were significantly lower in patients with poor or fair preparation (72.1% and 75.4%, respectively) than in those with good and excellent preparation (99.7% and 99.9%, respectively; P < 0.001), and significantly lower than the QI of 95% (P < 0.001). ADR in men and women combined was similar in all four grades of preparation (excellent, good, fair and poor) at 24.2% vs. 26.8% vs. 32.1% vs. 22.1%, respectively; P = 0.06. All the groups had ADR above the QI (25% for men and 15% for women) with evidence of significantly higher ADR in the women with excellent or good preparation and in men with excellent, good or fair preparation. On multivariate analysis, male gender was significantly associated with increased ADR (P < 0.001), while the quality of bowel preparation did not influence ADR. Conclusions: Patients with fair and poor standards of preparation have significantly lower colonoscopy completion rates than those with excellent and good preparation. However, there was no difference in ADR between the different grades of preparation.