The Impact of Split Dose of Low-volume Polyethylene Glycol on Adenoma Detection Rate

An adequate level of bowel preparation is crucial for the efficacy and safety of colonoscopy. Strong evidences suggest that bowel-preparation quality shows an inverse correlation with length of the interval between the end of cleansing agent intake and the start of colonoscopy (shorter intervals are associated with better preparation levels). Accordingly, the use of a split-dose administration regimen has been demonstrated to significantly improve the quality of preparation, besides patient acceptability, as compared with standard administration the day before colonoscopy. All randomized controlled trials comparing split versus standard preparations were primarily aimed at assessing the quality of colon cleansing, by means of either validated or not-validated colon cleansing scales. The impact of a split dose regimen on objective colonoscopy performance measures such as adenoma detection rate (ADR) has never been specifically and prospectively evaluated. The present study is aimed at evaluating whether the split-dose preparation regimen is associated with an increase of adenoma detection. For this purpose, asymptomatic subjects aged 50-69, undergoing screening colonoscopy for positive immunologic fecal occult blood test are randomized in a 1:1 ratio to receive low-volume (2L) PEG plus ascorbic acid solution either in a split-dose (study arm) or in a full-dose regimen (control arm). Treatments are allocated using a computer-generated, randomized code list. The treatment allocation is concealed and is accomplished at the screening visit through non-research personnel who is not involved in the study. To ensure masking, the endoscopists who perform the colonoscopies are not involved in the randomization process and in the pre-procedure data collection. In this study the the primary outcome measure was the proportion of patients with at least one adenoma (Adenoma Detection Rate) in each harm. Data on bowel cleansing, patient compliance, tolerability and acceptability were also collected. A sample size of at least 514 patients (257 in each arm) was calculated, by hypothesizing a relative increase of 25% in the adenoma detection rate in the split dose preparation group, assuming a 40% prevalence of one or more adenoma in FIT-positive patients undergoing screening colonoscopy (significance level 0.05, 90% power).