| Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
| Level II |
Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
| Level III | Other |
Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[1] Polyethylene glycol, oral: Park DI, Park SH, Lee SK, Baek YH, Han DS, Eun CS, Kim WH, Byeon JS, Yang SK. Efficacy of prepackaged, low residual test meals with 4L polyethylene glycol versus a clear liquid diet with 4L polyethylene glycol bowel preparation: a randomized trial. J GastroenterolHepatol. 2009 Jun;24(6):988-91. http://www.ncbi.nlm.nih.gov/pubmed/25053529
Sodium sulfate, oral: Johnson DA, Barkun AN, Cohen LB, Dominitz JA, Kaltenbach T, Martel M, Robertson DJ, Boland CR, Giardello FM, Lieberman DA, Levin TR, Rex DK. Optimizing adequacy of bowel cleansing for colonoscopy: recommendations from the U.S. multi-society task force on colorectal cancer. GastrointestEndosc. 2014 Oct;80(4):543-62. http://www.ncbi.nlm.nih.gov/pubmed/25220509
Sodium sulfate, oral: Di Palma JA, Rodriguez R, McGowan J, Cleveland M. A randomized clinical study evaluating the safety and efficacy of a new, reduced-volume, oral sulfate colon-cleansing preparation for colonoscopy. Am J Gastroenterol 2009;104:2275-84. http://www.ncbi.nlm.nih.gov/pubmed/19584830
Sodium sulfate, oral: Rex DK, Di Palma JA, Rodriguez R, McGowan J, Cleveland M. A randomized clinical study comparing reduced-volume oral sulfate solution with standard 4- liter sulfate-free electrolyte lavage solution as preparation for colonoscopy. GastrointestEndosc 2010;72:328-36. http://www.ncbi.nlm.nih.gov/pubmed/20646695