Eighty- two RCTs were included in the review (number of patients not reported).
Polyethylene glycol versus sodium phosphate (24 studies): The pooled efficacy, based on the endoscopist's assessment of preparation as good or excellent, showed no significant difference between the treatments (OR 1.00, 95% CI: 0.67 to 1.50; 21 RCTs). There were some discrepancies between the text and the forest plots. Statistically significant heterogeneity was detected (I2=81.7%). Sodium phosphate was reported as having better tolerability in 14 studies, no difference between groups was reported in 10 studies, while one study favoured polyethylene glycol.
Other studies of different bowel preparation regimes could not be combined statistically.
Different formulations of polyethylene glycol: Six studies assessed different electrolyte combinations. Apart from one which found a low-sulphate formulation to be associated with increased efficacy, there were no significant differences between the groups. No differences were reported with the addition of metoclopramide, bisacodyl, cisapride, senna or magnesium citrate. Six studies assessed the addition of simethicone, with five reporting improved visibility with the agent; two studies assessed tolerability with conflicting results. Eight studies that assessed low-volume polyethylene glycol found contradictory evidence for efficacy, but most found low volume regimes to have greater tolerability.
Different formulations of sodium phosphate: Seven studies found a dose-response relationship for efficacy and an inverse effect for tolerability. Two studies found that dose division reduced nausea without impacting efficacy.
Sodium picosulphate and magnesium citrate: Two trials compared sodium picosulphate plus magnesium citrate with polyethylene glycol, and two trials compared the combination with sodium phosphate. In the comparison with sodium phosphate, one trial showed better toleration and equivalent efficacy, the other trial showed better efficacy and equivalent tolerability. The same pattern of results was found in comparisons with polyethylene glycol.
Results of trials reporting biochemical measures of safety and measures of compliance were also reported.