• Cancer Prevention Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou 510060, China.
• Department of Medical Oncology, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou 510060, China.

Objective: To investigate the colonscopy screening interval among patients with negative colonscopy. Methods: We selected 14 606 participants who completed the baseline and 3-year or 5-year colonoscopy examinations in the American Prostate, Lung, Colorectal, and Ovarian (PLCO) dataset as the target population. Sociodemographic characteristics (i.e., sex, age, marital status, race, and smoking), lifestyle, family history of cancer, and family history of colorectal cancer were collected. Cochran-Armitage trend analysis was used to examine whether the rate of positive cases (colorectal cancer, advanced adenoma, adenoma, and hyperplastic polyp) was increased with the length of screening interval. We compared the differences in number of detected cases, positive rates, and proportions of 3-year and 5-year screening interval strategies using internal standardization method. Results: The age of the population was （61.9±5.2） years and over half of them were males (54.4%) and 46.2% had family cancer history. The mean screening interval between the first and second endoscopies was （1 639.1±320.9） days. A total of 1 716 cases had positive endoscopic findings. With the screening interval extended, rate of the screened positive cases was also increased (P _{for trend}<0.001). After standardized by the internal standardized population (14 606), 17.99 and 11.57 colorectal cancer cases and 177.37 and 240.35 advanced adenoma cases were detected by 3-year and 5-year screening interval strategies, respectively. Conclusion: Based on the initial screening negative population of colonoscopy in the United States, the 3-year screening interval strategy could detect a relatively large number of colorectal cancer cases, but its health and economic evaluation needs to be further explored.