In Focus

Quality metrics in colonoscopy


Editor's Note:

As quality metrics are becoming increasingly significant throughout all of medicine, our field is no exception. Recent evidence has demonstrated the importance of quality measures in colonoscopy; understanding, reporting, and improving these metrics has become a hot topic of discussion.

In this month’s In Focus article, brought to you by The New Gastroenterologist, Nabiha Shamsi, Ashish Malhotra, and Aasma Shaukat (University of Minnesota/Minneapolis VAMC) provide an outstanding overview of the evidence as well as recommended goals for important quality metrics in colonoscopy. Ultimately, improving colonoscopy quality amongst all gastroenterologists will increase colonoscopy value and lead to further decreases in the incidence and mortality of colorectal cancer.

Bryson W. Katona, MD, PhD
Editor in Chief, The New Gastroenterologist


Colonoscopy is a widely used modality to evaluate colorectal cancer because it allows for both identification of early malignancies and removal of precancerous lesions. The increased use of colonoscopy in the last 20 years has been associated with a decline in the incidence and mortality from colorectal cancer.1,2 However, colonoscopy has its limitations. It is an invasive test with inherent risks. Additionally, studies have reported rates of post-colonoscopy cancers, also referred to as interval cancers, of 2%-7%, and miss-rates for adenomas by tandem colonoscopy of 2%-26%.3-5

Table 1. Recommended goals of colonoscopy quality

High-quality exams can maximize the value of colonoscopy, and it is important to consider the factors that contribute to high-quality colonoscopies. While there are many metrics proposed,6,7 here we discuss the most evidence-based ones, outlined in Table 1, along with their goal values.

Cecal intubation rate

Dr. Ashish Malhotra

A high-quality colonoscopy should include a complete examination of the colon. To achieve this, it is necessary to fully intubate the cecum, passing the colonoscope past the ileocecal valve to examine the medial wall of the cecum.8

There are several factors that may contribute to an incomplete colonoscopy, including bowel preparation, anatomy, body habitus, and endoscopist’s skill. To calculate cecal intubation rate as a quality measure, colonoscopies that are incomplete because of poor bowel preparation, severe colitis, or known obstructing lesion are usually excluded.

The U.S. Multi-Society Task Force on Colorectal Cancer recommends a cecal intubation rate of at least 95% for screening colonoscopy and 90% for all colonoscopies.6 There is an expectation of photodocumentation of the ileocecal valve and appendiceal orifice to establish completion of the colonoscopy.6

Some methods used to assist with cecal intubation include changing patient position, applying abdominal pressure, stiffening the colonoscope, and alternating between adult or pediatric colonoscopes.

Adenoma detection rate

Adenoma detection rate (ADR), is defined as the proportion of patients over the age of 50 years undergoing first-time screening colonoscopies in which at least one adenomatous polyp is detected for a given endoscopist in a given time period.

Dr. Nabiha Shamsi

Adenomas are tracked because clearing the colon of neoplasm is the goal of screening colonoscopies; adenomas are tracked instead of more advanced lesions because the higher frequency of adenomas allows for better tracking of variation between endoscopists. Tracking ADR also utilizes the assumption that, if small lesions are identified, larger ones will be as well.

ADR is the only current quality indicator reported to be significantly associated with the risk of interval cancers. In 2010, a study of 45,000 screening colonoscopies by 186 endoscopists validated the use of ADR, finding that patients who underwent colonoscopy by physicians with ADRs below 20% had hazard ratios for development of postcolonoscopy cancer greater than 10 times higher than patients of physicians with ADRs above 20%.9 However, this study had limited power to establish that cancer protection continues to improve when ADRs rise above 20%. Another study, which evaluated the association of ADR in 224,000 patients undergoing colonoscopies by 136 gastroenterologists, showed each 1% increase in ADR is associated with 3% decrease in the risk of interval CRC and 5% decrease in the risk of fatal interval cancers.10

Most recent guidelines propose an adequate ADR for asymptomatic individuals aged 50 years or older undergoing screening colonoscopy should be greater than 30% in men and greater than 20% in women.6 It remains unknown whether there is a threshold for maximum benefit of ADR, in which a very high ADR is not associated with further protective benefit. The answer to this question may depend on why a low ADR is associated with a higher rate of interval cancers and whether every missed polyp, independent of size, is a potential interval cancer or whether hasty, inadequate, or incomplete examinations of the colon are the underlying concern.

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