What are the most important quality standards for colonoscopy?

Colonoscopy is an important screening procedure to detect and remove adenomas and polyps that can potentially lead to colorectal cancer. For several years, a high adenoma detection rate has been considered an important criterion for screening colonoscopy. To assess the quality of bowel preparation, the Boston Bowel Preparation Scale can be used.

Carcinoma of the colon or rectum (colorectal carcinoma) is the third most common cancer in men and the second most common cancer in women in Switzerland [1]. 4300 people are diagnosed with colon cancer in this country every year, and most of those affected are over 50 years old [1]. In Switzerland, mandatory health insurance covers two colonoscopies at an interval of ≥10 years or a fecal immunochemical test (FIT) at an interval of ≥2 years between the ages of 50 and 69. In case of a positive finding in the FIT, an endoscopic examination of the entire colon should be performed. Screening colonoscopy is used for early detection of colorectal cancer and resection of colon polyps. In high-risk patients and/or suspicious symptoms (overview 1) , colonoscopy may be indicated outside this age interval [2]. Colonoscopy with sampling biopsies has the highest sensitivity and specificity of all examinations and thus represents the diagnostic gold standard. That colonoscopy can reduce the incidence of colorectal cancer and mortality rates was shown, for example, in the non-randomized “closed cohort” study in Swiss mountain cantons [3]. And in Germany, the prevalence of colorectal cancer has decreased significantly in the 55-84 age group since the introduction of health insurance-approved screening colonoscopies in 2002: by 17-20% in men and 20-26% in women [4].

Adenoma Detection Rate (ADR)

According to WHO, effective screening measures should be documented through quality assurance [5,6]. A position paper of the European Society for Gastrointestinal Endoscopy (ESGE) lists the currently recommended “performance measures for lower gastrointestinal endoscopy” [7]. These are parameters that have been shown to be associated with better outcomes. In large cohort studies, adenoma detection rate (ADR) in particular was associated with both lower incidence and mortality of colorectal cancer [8,9]. The target ADR is 25%, based on the fact that a cut-off value of 24.6% was associated with the lowest colorectal cancer mortality [10,11].

Preparation quality: “Boston Bowel Preparation Scale” (BBPS)

Detection of adenomas is significantly dependent on visualization of the entire colonic mucosa. Therefore, in addition to high ADR, it is important to achieve adequate preparation quality and sufficient cecal coverage. For this purpose, the use of a validated scoring system is recommended, such as the Boston Bowel Preparation Scale(box) [12,13]. The preparation quality of the assessed colon should be at least intermediate [8, 14]. It is recommended to aim for a high rate of colonoscopies that are pre-scoped to the cecum, as a low cecal reach rate is associated with a higher incidence of colorectal carcinoma (both distal and proximal) [15]. Currently, the minimum standard is stated to be a cecal reach rate ≥90%, with a rate ≥95% considered optimal [16]. To ensure that polyps are completely ablated, ESGE specifies a guideline-compliant ablation rate of at least 80%. This means that polyps <10 mm should be ablated with the cold snare and ≥10 mm with the hot snare [17]. Inadequate polyp ablation technique is responsible for up to 25% of colorectal cancers after screening colonoscopy (post-colonoscopy colorectal cancer, PCCRC) [18].

Follow-up after polypectomy

Colonoscopy is considered a very safe procedure. Studies report a complication rate of approximately 0.3-0.5 per 1000 examinations [19]. Complications occurring during the examination and events occurring after colonoscopy, such as hospitalizations or 30-day mortality, must be documented according to ESGE [16]. Regarding patient compliance, it is important to minimize pain and discomfort during colonoscopy. While there is currently no established standard for patient satisfaction, experience has shown that effective sedation practices during colonoscopy can help improve patient experience [20]. After screening colonoscopy, proper management with any follow-up colonoscopies is essential. This is because only with adequate follow-up after polypectomy can any newly grown or incompletely resected polyps be removed. The European Society for Gastrointestinal Endoscopy recommends that patients in whom high-risk polyps have been detected should undergo a repeat colonoscopy after 3 years. In patients without high-risk polyps, another colonoscopy is considered reasonable after 10 years. The definition of high-risk polyps was updated in 2020 [21]. Accordingly, follow-up should only occur in patients who have at least one adenoma with high-grade dysplasia or a size ≥10 mm or in patients who have ≥5 adenomas or who have at least one serrated polyp with dysplasia or a size ≥10 mm.

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