A Study Between Two Instrument Generations to Improve Adenoma Detection in Screening Colonoscopy

Adenoma detection rate (ADR) is the most important parameter to measure outcome quality of (screening) colonoscopy. Since single improvements of imaging have not been able to improve ADR in many randomized studies, the present study tested the hypothesis that only multiple imaging improvements such as seen with two generation changes of colonoscopies - i.e. skipping one colonoscope generation - may be necessary before improvements in ADR can be measured.

The investigators will test this hypothesis in the present randomized tandem study in 7 private practices in Hamburg and Berlin, in a pure screening colonoscopy setting, aiming at inclusion of 1200 patients \> age of 55 years (screening colonoscopy cut-off in Germany). Exclusion criteria are symptomatic patients and colonoscopies planned for therapeutic reasons. Main outcome parameter is the ADR (rate of patients with at least one adenoma/all patients).

The study was a prospective multicenter randomized study involving 7 private practice gastroenterology offices with a total of 14 experienced examiners (\> 2000 colonoscopies), performed between November 2013 and September 2016 (sets of instruments were made available to 3-4 centers each during 6-12 months).Study population:

Patients were selected from the screening colonoscopy list (age ≥ 55 years), with further inclusion criteria being status 1 and 2 of the ASA classification. After informed consent, patients were randomized using sealed envelopes per center to one of either of the two study groups

1. 190 C group (intervention group), examination with the latest generation colonoscope (190 series CF or PCF colonoscopies, Olympus Corp, Hamburg, Germany).
2. 165 C group (control group), examination with the 160/5 generation colonoscope (Olympus Corp, Hamburg, Germany), Each patient underwent bowel preparation in accordance with local practice of the centers. Bowel cleansing quality was segmentally assessed using a modified overall "Boston Bowel Preparation Scale". Introduction and withdrawal times were measured, and times required for biopsies and polypectomies were considered separately, i.e. overall and diagnostic only withdrawal times were recorded separately.

Polyps were documented with regards to location (caecum, ascending, transverse and descending colon, sigmoid and rectum), size and morphology using the Paris classification (polypoid pedunculated or sessile, non-polypoid slightly elevated/flat/depressed, ulcerous). Polyps were then resected using biopsy forceps or cold snare or conventional polypectomy according to local standards. Histology of resected polyps was analyzed by local private practice specialized GI pathologists according to the Vienna classification with regards to dysplasia grade and the presence of serrated adenomas; final histologic categories were hyperplastic, adenomatous \[tubulous, villous, tubulovillous, serrated (traditional or sessile serrated)\]. Small distal rectal polyps were not systematically biopsied or resected, due to a very high likelihood to be hyperplastic.

Eligibility Criteria:
Inclusion Criteria:

* screening colonoscopy, age ≥ 55 years
* status 1 and 2 of the ASA classification
* signed informed consent

Exclusion Criteria:

* Symptoms indicative of colorectal disease such as colonic bleeding, significant diarrhea, obstipation and change in bowel habits
* Known colonic disease for further evaluation (e.g. inflammatory bowel disease, polyps for resection)
* Surveillance after polypectomy or colon tumor surgery
* Anticoagulants preventing biopsy or polypectomy
* Poor general condition (ASA III or more)
* Incomplete colonoscopy planned