Colonoscopy Quality Indicators Differ in the Proximal and Distal Colon

Abstract

Purpose: Colonoscopy with polypectomy is associated with a reduction in colorectal cancer of the distal colon, but appears to be less protective for lesions of the proximal colon. The adenoma detection rate (ADR) is a validated measure of quality in colonoscopy. Polypectomy detection rate (PDR) has been proposed as a surrogate marker for ADR, demonstrating correlation with ADR in retrospective studies. The aim of this study was to evaluate PDR and ADR separately in the proximal and distal colon. Methods: We reviewed a colonoscopy database for outpatient procedures performed over a 6-month period by 20 gastroenterologists of a single academic medical center. Quality measures including ADR, PDR, mean adenomas per patient (MAP), mean polyps per patient (MPP) and advanced neoplasia detection rate (ANDR) were calculated. Procedures identifying 3 or more adenomas per patient (≥3DR) were also noted. The ratio of adenomas detected to polyps removed (adenoma/polyp ratio) was calculated. ADR and PDR were compared for lesions of the proximal versus distal colon (splenic flexure and below). Data were compared using the Chi-square test. Results: A total of 1921 colonoscopies were performed during the study period. ADR was 31% (13%-42%). ADR was significantly higher in men (36%) compared to women (26%), and in surveillance (47%) compared to screening studies (29%) (p < 0.001). PDR was 49% (16%-64%). PDR was significantly higher in men (63%) than in women (35%) (p < 0.001). The adenoma/polyp ratio was 0.49 (0.29-0.81). MAP was 0.58 (0.27-0.96) and MPP was 1.19 (0.27-1.71). Each measure was lower in the subset of screening colonoscopies (0.50 vs.0.58, p= 0.011 and 1.04 vs. 1.19, p< 0.001). ≥ 3DR was 5.4%, and ANDR was 6.7%. Colorectal cancer was detected in 10 patients (0.52%). In terms of distribution, 1038 polyps (corresponding to 753 adenomas) were removed from the proximal colon, and 1248 polyps (corresponding to 372 adenomas) were removed from the distal colon. Proximal PDR was significantly lower than distal PDR (26% vs. 32%, p= 0.05). Conversely, proximal ADR exceeded distal ADR overall (23% vs. 14%, p< 0.001) and in screening studies (19% vs. 14%; p = 0.016). Conclusion: Quality measures such as ADR and MAP varied amongst endoscopists. Higher ADR did not correlate with endoscopist's volume, patient gender, % surveillance, or withdrawal time. Adenoma/polyp ratio also varied, and PDR was not a consistent correlate of ADR in this study. The majority of adenomas were located in the proximal colon. Proximal polyps were more likely to be adenomas, compared with distal polyps. Proximal PDR may be a better surrogate marker compared with overall PDR for the detection of precancerous lesions of the colon.Table: Proximal and distal ADR and PDRTable: Table. Adenoma vs. polyp detection and other quality measures