Background and Aims There is controversy about the length of low‐residue diet (LRD) for colonoscopy preparation. The aim of the study was to compare one‐day vs. three‐day LRD associated to standard laxative treatment for achieving an adequate colonoscopy preparation in average risk subjects with positive fecal immunochemical test undergoing screening colonoscopy. Methods A non‐inferiority, randomized, controlled, parallel‐group clinical trial was performed in the setting of average risk colorectal cancer screening program. Participants were randomized to receive 1‐day vs. 3‐day LRD in addition to standard polyethilenglicol treatment. Adequacy of preparation was evaluated using the Boston Bowel Preparation Scale (BBPS). Primary outcome was achieving a BBPS ≥ 2 in all colon segments. Analysis was performed for a non‐inferiority margin of 5%, a 95% statistical power and one‐sided 0.05 significance level. Results A total of 855 patients were randomized. Adequate bowel preparation was similar between groups: 97.9% of patients in the 1‐day LRD group vs 96.9% in the 3‐day LRD group achieved the primary outcome (P‐value for non‐inferiority < 0.001). The percentage of patients with BBPS scores ≥ 8 was superior in the 1‐day LRD group (254 vs 221 in the 3‐day LRD group, P = 0.032). The 1‐day regimen was better tolerated than the 3‐day diet. 47.7% (vs 28.7%, P < 0.05) of patients rated the 1‐day LRD as very easy to follow. Conclusion The 1‐day LRD is non‐inferior to 3‐day LRD for achieving an adequate colon cleansing before average risk screening colonoscopy and it is better tolerated.

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Background Patient satisfaction or experience with colorectal cancer screening can determine adherence to screening programs. An evaluation of validated patient reported outcome measures (PROMs) for measuring experience or satisfaction with colorectal cancer screening does not exist. Our objective was to identify and critically appraise validated questionnaires for measuring patient satisfaction or experience with colorectal cancer screening. Methods We conducted a systematic review following the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology. We conducted searches on MEDLINE, EMBASE, PsychINFO, CINAHL and BiblioPRO and assessed the methodological quality of studies and measurement properties of questionnaires according to the COSMIN guidelines for systematic reviews of PROMs. PROSPERO registration number: CRD42019118527. Results We included 80 studies that used 75 questionnaires, of which only 5 were validated. Four questionnaires measured satisfaction with endoscopy: two in the context of colorectal cancer screening (for colonoscopy and sigmoidoscopy) and two for non-screening endoscopy. One questionnaire measured satisfaction with bowel preparation. The methodological quality of studies was variable. The questionnaires with evidence for sufficient content validity and internal consistency were: the CSSQP questionnaire, which measures safety and satisfaction with screening colonoscopy, and the Post-Procedure questionnaire which measures satisfaction with non-screening endoscopic procedures. Conclusions This systematic review shows that a minority of existing PROMs for measuring patient satisfaction with colorectal cancer screening are validated. We identified two questionnaires with high potential for further use (CSSQP and the Post-Procedure questionnaire).

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