Meta-analysis and cost comparison of polyethylene glycol lavage versus sodium phosphate for colonoscopy preparation

Although polyethylene glycol lavage solutions are widely used for colonoscopy preparation, evidence suggests that sodium phosphate is better tolerated and has similar efficacy. The purpose of this study was to compare compliance with and efficacy of polyethylene glycol and sodium phosphate using meta-analysis and to compare the cost of colonoscopy with both methods.

We used Medline to identify all randomized controlled trials comparing the two preparations. Study methods were evaluated, and quantitative data were abstracted independently, including inability to complete the preparation and preparation quality, rated as adequate or excellent. A random effects model was used to calculate the pooled relative risk. Direct costs and literature-based probability estimates were used to compare costs.

Among 1286 subjects from eight colonoscopist-blinded trials, the pooled relative risk of inability to complete the preparation was 0.23 (95% CI [0.18-0.28]) in favor of sodium phosphate. Although the best estimate of the relative risk for an adequate quality preparation revealed therapeutic equivalence (relative risk = 1.06: 95% CI [0.95-1.19]), an excellent quality preparation was more likely with sodium phosphate (relative risk = 1.72: 95% CI [1.16-2.53]). Assuming reexamination rates from published literature of 3% and 8% for sodium phosphate and polyethylene glycol, respectively, direct costs of colonic examination were $465 and $503. There were no clinically important adverse effects with either method.

The results suggest that sodium phosphate is as effective and less costly, with a more easily completed preparation, compared with polyethylene glycol and is the preferred method of preparation for colonoscopy for certain patient subgroups.