3-day vs. 1-day Low Residue Diet Influence in Colonoscopy Preparation and Patient Tolerability

a. Study type: prospective, randomized, single-blinded trial: i. Prospective inclusion of ambulatory patients; ii. Randomization by computer generated tables; iii. Allocation concealment by sealed, opaque envelopes; iv. Patient not blinded to diet; v. Endoscopist blinded to the diet followed by each patient. b. Patient selection: Consecutive series of patients scheduled for total colonoscopy; Exclusion criteria: inpatients, sedation, urgent procedures, colonoscopies not intended to reach the caecum, patient with previous partial colectomy. c. Sample Size: i. 412 individuals; 2 groups of 206 patients ii. Primary goal: to achieve a reduction from 15 to 5% of inappropriate preparation result; The Boston Bowel Preparation Scale (BBPS) will be used as grading system. Inappropriate is defined as total BBPS \< 6 or \< 2 in any segment. The chosen scale is the most systematically validated and appropriate for the clinical setting. iii.Both groups, from a community-based outpatient ambulatory center, used the same split dose regimen with Polyethylene glycol (PEG).Patients were instructed to drink 3 L of PEG preparation on the afternoon of the day prior to the exam and 1 L four hours before the scheduled exam time. All the exams scheduled for morning period. Assuming a normal distribution, a power of 90% and a type I error of 0.05, the calculated sample size for each group was 188; allowing a 10% dropout rate, the sample size is 206 per group (412 patients overall); Groups: Group A: 3-day low residue diet + split dose preparation; Group B: 1-day low residue diet + split dose preparation d. Endoscopist: Exams to be conduct by 5 board-certified gastroenterologists and 2 supervised fellows in training; All physicians were trained in the use of BBPS by online training available at http://cori.org/bbps/, and have been using the BBPS for at least 3 months. e. Data collection methods: form sheet filled by the endoscopist and patient opinion regarding the assigned bowel preparation protocol. f. Analyzed variables: i. Primary outcome: BBPS score ii. Secondary outcome: Patient assessment of tolerance and acceptance of the preparation and diet iii. Tertiary outcome: polyp detection rate (PDR), polyp location, size and configuration; adenoma detection rate (ADR), cecum intubation rate iv. Other variables and patients characteristics (age, gender, chronic medication, risk factors for inappropriate preparation), withdrawal time. g. Statistical analysis: T-test for groups comparing quantitative variables with normal distribution (primary outcome); Qui square test for groups comparing proportions (secondary and tertiary outcomes)