Characteristics of included studies.

Objective
To evaluate the effect of telephone instructions on the quality of bowel preparation in patients undergoing colonoscopy.
Methods
Online English databases (PubMed, Web of Science, Cochrane Library, and Embase) were screened for randomized controlled trials on telephone instructions regarding bowel preparation for colonoscopy from inception to April 15, 2022. After data extraction, the Review Manager software was used for meta-analysis.
Results
Nine randomized controlled trials with 3,836 patients were included in the meta-analysis. The rate of adequate bowel preparation was significantly higher in the telephone group than in the control group. The pooled relative risk (RR) was 1.17 (95% confidence interval [CI]: 1.05–1.30, P < 0.01). The pooled mean difference (MD) for the Boston Bowel Preparation Scale score was 1.32 (95% CI: 0.15–2.49, P < 0.05), and that for the Ottawa Bowel Preparation Scale score was −1.93 (95% CI: −2.35 to −1.51, P < 0.01). The polyp detection rate was significantly higher in the telephone group than in the control group (RR = 1.58, 95% CI: 1.23–2.04, P < 0.01), whereas no significant difference was noted in the adenoma detection rate between the groups (RR = 1.37, 95% CI: 0.97–1.94, P = 0.08).
Conclusion
Telephone instructions for patients undergoing colonoscopy significantly improved the quality of bowel preparation and increased polyp detection rate.