Monitoring colonoscopy withdrawal times remains important

We read the recent paper on colonoscopy withdrawal time (CWT) with interest [1]. In the English Bowel Cancer Screening Programme, a diagnostic withdrawal time of at least 6 minutes remains a key quality metric for colonoscopic performance [2]. We feel that it is an important standard, as it helps to protect against the poor practice of rapid withdrawal without proper mucosal inspection. Although a slow withdrawal time is not the only aspect of a gold standard inspection technique, it remains one of its key principles.

In their introduction, the authors quote two papers supporting their argument that withdrawal time is not a useful quality indicator [3] [4]. However it is important to point out that in the study by Taber & Romagnuolo there was a statistically significant correlation between polyp detection rate and longer procedure time. Likewise in the study by Gellad et al., there was a significant correlation between CWT and adenoma detection rate (ADR). Moreover, in Moritz et al.’s study colonoscopists with a longer median CWT had a 21 % greater ADR, although this did not reach statistical significance (odds ratio [OR] 1.21, 95 % confidence interval [CI] 0.94 – 1.56; P = 0.14). Also, 85 % of colonoscopists in this study already had a median CWT of more than 6 minutes. Although this was a large study, this may represent a type II error, particularly given that other studies have shown a positive correlation.

As a standard, colonoscopic withdrawal time is particularly useful in two situations:

1. As a supportive/explanatory tool when an individual’s adenoma detection rate falls below (or is close to) the agreed standard – we have often found that this allows the colonoscopist to reflect on and adjust their extubation technique.

2. As a quality indicator for diagnostic technique in patient cohorts where the adenoma detection rate standard is either not appropriate or cannot be applied – for example colitis surveillance or if an individual’s practice comprises predominantly young patients.

We, like others, have found a clear correlation between a slow inspection of the mucosa on extubation and adenoma detection rate [5]. We feel it is important for good colonoscopic practice to uphold this valuable principle of diagnostic technique and quality metric.

• References

• 1 Moritz V, Bretthauer M, Ruud HK et al. Withdrawal time as a quality indicator for colonoscopy – a nationwide analysis. Endoscopy 2012; 44: 476-481
• 2 Chilton A, Rutter M. Quality assurance guidelines for colonoscopy. NHS BCSP Publication No 6. Sheffield, UK: NHS Cancer Screening Programmes. 2.10, p. 9 Available at: 2011 http://www.cancerscreening.nhs.uk/bowel/publications/nhsbcsp06.pdf
• 3 Taber A, Romagnuolo J. Effect of simply recording colonoscopy withdrawal time on polyp and adenoma detection rates. Gastrointest Endosc 2010; 71: 782-786
• 4 Gellad ZF, Weiss DG, Ahnen DJ et al. Colonoscopy withdrawal time and risk of neoplasia at 5 years: results from VA Cooperative Studies Program 380. Am J Gastroenterol 2010; 105: 1746-1752
• 5 Lee TJW, Blanks RG, Rees CJ. , on behalf of Northern Region Endoscopy Group (NREG) et al. Colonoscopy withdrawal time and adenoma detection rate in screening colonoscopy: the optimum average withdrawal time is 10 min. Gut 2011; 60 (Suppl. 01) A44