This is a prospective randomised trial comparing the proximal adenoma detection rate and miss rate by blue laser imaging (BLI), narrow band imaging or white light colonoscopy.

Study population:

Consecutive adult patients, age 40 or above, undergoing outpatient colonoscopy in the Queen Mary Hospital are invited to participate in this prospective randomized study. Patients are excluded if they are unable to provide informed consent or have undergone previous colorectal resection, or have personal history of colorectal cancer, inflammatory bowel disease, familial adenomatous polyposis, Peutz-Jeghers syndrome, or other polyposis syndromes. Patients who are considered to be unsafe for polypectomy including patients with bleeding tendency and those with severe comorbid illnesses will be excluded. In addition, patients are excluded post-randomization if either the cecum could not be intubated for various reasons or Boston Bowel Preparation Scale (BBPS) score is <2.

Study design and randomization:

This is a prospective randomized crossover trial comparing the proximal adenoma detection rate and miss rate of BLI (ELUXEO endoscopic system) vs NBI (290 video system) vs WLI which is conducted in the Endoscopy Center of the Queen Mary Hospital of Hong Kong. Eligible patients are randomly allocated to four groups in a 1:1:1 ratio to undergo tandem colonoscopy of the proximal colon, defined as cecum to splenic flexure. The three groups are: (1) NBI follow by WLI; (2) BLI follow up WLI; (3) WLI follow by WLI. Randomization will be carried out by computer generated random sequences and stratified according to endoscopist's experiences (experienced versus fellows) and indications of colonoscopy (symptomatic vs screening/surveillance). All procedures are performed with high-definition endoscopes. The patients are blinded to the group assignment.

Inclusion Criteria:

• Age 40 or above
• scheduled for colonoscopy

Exclusion Criteria:

• unable to provide informed consent
• have undergone previous colorectal resection,
• personal history of colorectal cancer, inflammatory bowel disease, familial adenomatous polyposis, Peutz-Jeghers syndrome, or other polyposis syndromes.
• Patients who are considered to be unsafe for polypectomy including patients with bleeding tendency and those with severe comorbid illnesses
• poor bowel preparation