Reproducibility and accuracy of visual estimation of polyp size in large colorectal polyps

Abstract

Background: Previous studies indicate that visual size estimation (in situ) of polyp size tends to differ from postfixation measurements, which effects allocation to surveillance intervals. Little is known about interobserver variation of in-situ measurements of large polyps. The primary objective was to assess interobserver variation of in situ measurements of large colorectal polyps. Secondary objectives were the agreement of in situ measurements with postfixation measurements, and the agreement on detection of !20 mm polyps between these measurements. Material and methods: Interobserver variability of in situ polyp size measurements was assessed between a diagnostic colonoscopy and the secondary therapeutic colonoscopy by dedicated endoscopists, in patients that were referred for an advanced polypectomy. After excision pre-and postfixation polyp sizes were measured with a ruler in three dimensions. Results: A total of 40 patients, with 45 polyps, were included in the study. The average difference between the two in situ measurements was 2.4 mm (95% confidence interval (CI): À0.4-5.2). The differences between the first in situ, second in situ and pre-fixation measurement in comparison to postfixation measurements were 1.8 mm (95% CI: À1.2-4.9), 0.1 mm (95% CI: À1.5-1.8) and 1.0 mm (95% CI: À0.2-2.2). Cohen's Kappa on detection of !20 mm polyps in agreement with postfixation measurements was 0.65 in the primary and 0.88 in the secondary in situ measurements. Conclusion: This study shows a variation between in situ size measurements of large polyps. Improvements in daily clinical routines can be made by using an instrument to compare polyp size with and refraining from rounding sizes up or down. A randomized controlled trial assessing which instruments should be used for in-situ measurements of large polyps is warranted, in order to optimize size measurements of large colorectal polyps.

Diagnostic accuracy of capsule endoscopy compared with colonoscopy for polyp detection: systematic review and meta-analyses

“…For instance, Parodi et al [16] considered patients as false positives if CCE estimated a lesion ≥ 6 mm but colonoscopy estimated the lesion to be ≤ 5 mm, which again skews the results negatively for CCE. However, studies show that even in situ measurements of polyp size vary between trained observers [31].…”

Post-polypectomy colonoscopy surveillance: European Society of Gastrointestinal Endoscopy (ESGE) Guideline – Update 2020

“…Surveillance interval recommendations depend strongly on polyp size, but measurement bias is present with evaluation both at endoscopy [34] and pathology [35]. It is known that at endoscopy size estimation is usually biased towards specific numbers (i. e., 5 or 10) while neglecting the others [34 -36], and interobserver variability in visual polyp sizing can be present [37,38], resulting in routine underestimation or overestimation of polyp size [39,40]. However, such bias can be reduced by using a reference standard, such as an open biopsy forceps or snare [41 -43].…”

Usefulness of a Colonoscopy Cap with an External Grid for the Measurement of Small-Sized Colorectal Polyps: A Prospective Randomized Trial

“…However, it is difficult to accurately measure polyp size. Although pathologic size measurement has been the “gold standard”, it is not always precise due to incomplete polyp resection; piecemeal resection of polyps, especially using forceps; postfixation deformity of extracted polyps; and interobserver variation of in situ measurements [ 20 , 21 ].…”